THE MORPHOLOGY OF BACTERIA.

Contribution à l'Étude de la Morphologie et du Développement des Bactériacées. Par A. Billet, Doct. en Méd., Médécin-Major de 2o classe. (Paris: Octave Doin.)

SINC

INCE the publication of the "Peach-coloured Bacterium," by Prof. Lankester, the subject of the morphology of the bacteria cannot be said to have received much attention from English investigators. The department of bacteriology has to a great extent been monopolised by the physician, who appears to confine himself almost exclusively to the study of the more practical bearings of the subject. It is therefore refreshing to find a surgeon-major devoting his time to a very thorough investigation of bacterial morphology.

Dr. Billet's work dates back from 1885, and was carried on for the most part in the Wimereux Laboratory under the able direction of Prof. Giard. His communications were first published in the Bul. Sc. de la France et de la Belgique, and the present work is a collected and revised edition of these. The work consists of some 287 pages, and includes (1) an historical introduction, which,

owing to its succinctness and chronological sequence, will be found of great use to the general bacteriologist; (2) a minute description of the life histories of Cladothrix dichotoma and Bacterium parasiticum, and of two new species named by Dr. Billet, Bacterium Balbiani and Bacterium osteophilum; (3) a very large bibliographical index embracing some 662 references; (4) a very beautiful series of drawings.

The author briefly sketches the progress of morphology from the time of the doctrine of immutability of Cohn and that of pleomorphism of Prof. Lankester, Cienkowski, and Zopf. He shows how C. Robin (1847), in his wonderfully interesting work, pointed to an affinity between certain bacteria, his Leptothrix baccalis, for instance, and certain filamentous algæ, the Leptothrix of Kützing (1843); how, after the lapse of twenty-six years, Prof. Lankester (1873 and 1876), determined, in his wellknown Bacterium rubescens, the coexistence of micrococcal, bacillary, and spirillar forms; and finally, how the theory of the "form phases" became further elucidated by Cienkowski in 1887 in the "Morphologie der Bakterien," and by Zopf in 1871 in his "Genetische Zusammenhang von Spaltpilzformen." The latter observer describes in the life history of the higher bacteria, coccal, bacteroid, bacillary, vibrio, spirillar, leptothrix, and zooglea forms; the Clathrocystis roseo-persicina of Cohn becomes the zooglea phase described in Bacterium rubescens of Lankester, or more correctly, of the higher Beggintoa roseo persicina. Starting with the above series of form phases, the author ingeniously consolidates and groups them into four stages, viz. :—1. The filamentous, which the bacteria are associated into larger and shorter filaments. 2. The dissociated stage in which the elements become free and motile, and assume the well-known coccal bacteroid and other forms. 3. The interlacing stage--état enchevêtré—where the elements interlace with one another. 4. A zooglea stage, in which the elements loose their movements and aggregate themselves into certain definite forms. The author goes on to show how definite and characteristic

in

are these groupings in the case of the organisms which he has examined (see above). He points out that their presence or absence depends upon surrounding conditions -media, temperature, &c. But he further widens the whole question in seeking to show that in the less highly developed bacteria there are traces of the form phases organisms. In this connection he briefly brings together and form groupings of the more morphologically perfec: the observations which have been made upon the life history of the lower bacteria. Thus the encapsulation observed in the pneumococci, streptococci, tubercle, and anthrax bacilli, sarcinæ, &c., &c., may correspond to the Zooglea stage, for he recognises both pneumococcal. merispomedia, and sarcina forms in his zooglea stage He regards the zooglea as protective, and forming when the medium is becoming exhausted. We may add that in the animal tissues encapsulation often appears dependent upon the resistance offered by the tissues. He further points out that the zooglea is often pigmented.

In describing the life histories of his bacteria, Dr. clined to believe that the cilium of the vibrio form is Billet makes some interesting remarks. Thus, he is innothing else than the residuum of the inner coat, and that it is formed during the process of segmentation by a drawing out and attenuation of the inner coat, like, for example, when a glass rod is drawn out in a flame. As many vibrios move about which have no cilia, he agrees with Van Zieghem that the bacterial element has a proper movement of its own, which is not dependent upon a cilium, and he believes that the cilium of the Bacteria is

quite a different thing from the cilium of zoospores. He carefully describes the movements of the vibrio forms, and adds that they are greatly accentuated by a powerful light, a point first observed by Engelmann, in his Bacterium photometricum. He also states that the passage from the rectilinear forms to the less curved (vibrio, and more curved (spirilla) forms, depends upon the degree of temperature and amount of putrefaction; the greater the latter the more the twisted and appendiculate forms. He concludes by giving the evidence in favour of a relationship between the Bacteria and the Alga; the relationship appears great in the case of the or ganisms which he describes, but probably if he had studied Actinomyces he might have similarly found very many points in favour of a relationship with the mycelial fungi.

RUBERT BOYCE

OUR BOOK SHELF.

Introductory Modern Geometry of Point, Ray, and Circle. By W. B. Smith. (London: Macmillan and Co., 1893.)

THIS work of Prof. Smith's has a "very practica! purpose," viz. "to present in simple and intelligible form a body of geometric doctrine, acquaintance with Freshman class" of the Missouri State University. It which may fairly be demanded of candidates for the is shaped on the lines of such modern works as those by Newcomb, Halsted, and Dupuis, to refer to English textbooks only; but it most nearly resembles in some parts the excellent little manual "on congruent figures," by Prof. Henrici. "The work asks to be judged, at least in its name, according to (the) spirit of modern geometry, and not according to the letter."

It is hard at this date to write anything new on the subject of elementary geometry, and for the class addressed by the author it is not desirable, but the wellknown facts may be treated in very diverse ways: in this case there is a novelty and freshness which must commend the treatment of them to all intelligent students. Take this "precise definition" of a plane: Take two points A and B and suppose two equal spherical bubbles formed about A and B as centres. Let them expand, always equal to each other, until they meet, and still keep on expanding. The line where the equal spherical bubbles, regarded as surfaces, meet, has all its points just as far from A as from B. As the bubbles still expand, this line, with all its points equidistant from A and B, itself expands and traces out a plane as its path through space. Hence we may define the plane as the region (or surface) where a point may be, that is, equidistant from two fixed points... It is evident that the plane, as thus defined, is reversible... The superiority of this definition consists in its not only telling what surface the plane is, but also making clear that there actually is such a surface. Thence our author readily derives the notion of the ray (anglicè, straight line: a tract being a part bounded by end points). This manner of illustration occurs repeatedly, and adds, we think, much to the interest of the book.

As a specimen of the mode of proof employed we take what is equivalent to part of Euc. i. 5. Data. ABC, an isosceles triangle, AB its base, AC and BC its equal sides (here we may remark the figure is badly drawn: a similar remark applies to figures on pp. 60 and 91). Proof. Take up the triangle ABC, turn it over, and replace it in the position BCA. Then the two triangles ACB and BCA have the equal vertical angles, C and C, also the side AC BC (why ?) and BC AC (why?); hence they are congruent (why?), and the A= = < B. In the more elaborate proofs there is a larger crop of "whys," and in some cases the interrogation is answered by the author.

=

=

The amount of ground covered is considerable, and yet, as we have gone through the whole of the text, it is so clearly opened up that the intelligent student, to whom we have previously referred, should be able to master it all, and successfully grapple with the well-chosen exercises which are arranged in fitting places throughout the book. "These exercises have been chosen with especial reference not so much to their merely disciplinary as to their didactic value, the author being persuaded that quite as good exercise may be found in going somewhither as in walking round the square."

We have no hesitation in heartily commending Prof. Smith's introduction to teachers and pupils as an excellent one, and this we vouch, adapting the language of the learned counsel cited by Bailie Littlejohn, nostro periculo. Primer of Horticulture. By J. Wright. (London: Macmillan and Co., 1893.)

THIS primer contains the substance of ten lectures delivered by Mr. Wright for the Surrey County Council. Besides the lectures, some sets of questions, asked after the lectures, are given together with the answers to these questions.

The primer is eminently practical, and is sure to prove very useful both to gardeners and to students. It cannot, however, be considered quite free from errors, and a careful revision would increase its value.

Sometimes the text is rather loose.

On p. 54 the word pistil is used indefinitely, sometimes meaning the style and at others the whole gynoecium. Speaking of phosphatic manures on p. 64 the author says:

"Mineral superphosphate is ground coprolite treated with sulphuric acid.

"Coprolite is antediluvian petrified manure, of which

there are large beds in the Eastern Counties. It is fairly active, yet sustaining. "Thomas's phosphate powder, or basic slagis composed of 15 to 25 per cent. of phosphoric acid and about 45 per cent. of lime. It is not very quick in action, but lasting in effect."

From this description one cannot get much idea of the relative values of these three phosphatic manures, and basic slag suffers by comparison with ground coprolite. Practical experience shows that basic slag has a much higher value than ground coprolite as a manure, and has, moreover, an additional value as a check upon wireworm. Again, on p. 77, the description of the fungus causing potato disease (phytophthora infestans) is scarcely accuIn describing the aerial hyphæ which spring from the mycelium in the leaves and push their way through the stomata, the author says:

rate.

"These stem-growths of the fungus produce 'fruit'spores (DD) in cells (Oogonia), that divide (F) and liberate the active agents in reproduction, tailed zoospores (G) which float in the air, and swim in the moisture, dew, or rain, on potato leaves." The letters in parentheses refer to fig. 18, p. 79. Neither text nor description below fig. 18 is correct. What Mr. Wright calls oogonia are really conidia, and what he calls conidia (F in fig. 18) represent the formation of an oospore from oogonium and antheridium. We must also dissent from the author's views on zoospores floating

in the air.

Apart from these defects the primer is well worthy of perusal, and will no doubt meet with success. The practical part is very well done, and this is, of course, the most essential part of the book. WALTER THORP. Ornithology in relation to Agriculture and Horticulture. Edited by John Watson. 220 pp. (London: W. H. Allen, 1893.)

THIS book contains a series of papers by well-known writers. The chief interest will gather around chapters iii. to vii. inclusive, which treat of the common sparrow. The trial of the sparrow is opened very ably by Mr. Chas. He is well supported Whitehead (for the prosecution). in the next chapter by Miss Eleanor A. Ormerod. These two writers for the prosecution will have the support of the vast majority of agriculturists in England, and their arguments contrast favourably with the less practical defence put forward in the two succeeding chapters by the Rev. F. C. Morris and the Rev. Theodore Wood.

Chapter VII. is written by J. H. Gurney, Jun., and from the result of 755 dissections he draws up a table showing that "in England about 75 per cent. of an adult sparrow's food is corn, chiefly barley and wheat, with a fair quan tity of oats." Nobody with experience of grain-growing in England will deny that the sparrow is a terrible pest, and it is time that a movement be made not towards exterminating the troublesome bird, but towards reducing its numbers to normal limits.

Chapter IX. is an interesting defence of the rook, much of which defence this bird merits. It is written by O. V. Aplin, who also contributes a very useful chapter on miscellaneous small birds. WALTER THORP.

LETTERS TO THE EDITOR. [The Editor does not hold himself responsible for opinions ex pressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]

Vectors versus Quaternions.

HAVING a vivid recollection of the pleasure I derived from Prof. Gibbs's attacks upon the quaternionic system in the rather one-sided discussion that took place about two years ago in this

journal, I have delayed replying to the letters of Profs. MacAulay and Tait, from an expectation that Prof. Gibbs would have something to say. In this I have not been mistaken; and, as there is a general agreement between us on the whole, I have merely to add some supplementary remarks. Prof. MacAulay refers to me as having raised the question again. I can assure him it has never been dropped. Apart from the one-sided dis. cussion, it has been a live question with Prof. Gibbs and myself since about 1882, and is now more alive than ever. I cannot help thinking that Prof. MacAulay's letter was overhastily written, and feel sure that if he knew as much about the views and methods of those to whom he appeals as he does about Quaternions, he would have written it somewhat differently, or perhaps not have written it at all, from a conviction of the uselessness of his appeal. There is no question of suicide with us; on the contrary, quite the reverse. I am asked whether the "spoonfeeding," as he terms it, of Maxwell, Fitzgerald, &c., is not good enough for me. Why, of course not. It is quaternionic, and that is the real point concerned. Again, he thinks nothing of the inscrutable negativity of the square of a vector in Quaternions; here, again, is the root of the evil. As regards a uniformity of notation amongst antiquaternionists, I dare say that will come in time, but the proposal is premature. We have first to get people to study the matter and think about it. I have developed my system, such as it is, quite independently of Prof. Gibbs. Nevertheless, I would willingly adopt his notation (as I have adopted his dyadical notion of the linear operator) if I found it better. But I do not. I have been particularly careful in my notation to harmonise as closely as possible with ordinary mathematical ideas, processes, and notation; I do not think Gibbs has succeeded so well. But that matters

little now; the really important thing is to depose the quaternion from the masterful position it has so long usurped, whereby the diffusion of vector analysis has been so lamentably impeded. I have been, until lately, very tender and merciful towards quaternionic fads, thinking it possible that Prof. Tait might modify his obstructive attitude. But there is seemingly no chance of that. Whether this be so or not, I think it is practically certain that there is no chance whatever for Quaternions as a practical system of mathematics for the use of physicists. How is it possible, when it is so utterly discordant with physical notions, besides being at variance with common mathematics? A vector is not a quaternion; it never was, and never will be, and its square is not negative; the supposed proofs are perfectly rotten at the core. Vector-analysis should have a purely vectorial basis, and the quaternion will then, if wanted at all, merely come in as an occasional auxiliary, as a special kind of operator. It is to Prof. Tait's devotion to his master that we should look for the reason of the little progress made in the last 20 years in spreading vector-analysis.

66

Now I have, in my turn, an appeal to make to Prof. MacAulay. I have been much interested in his recent R. S. paper. As the heart knoweth its own wickedness, he will not be surprised when I say that I seem to see in his mathematical powers the 'promise and potency" of much future valuable work of a hard-headed kind. This being so, I think it a great pity that he should waste his talents on such an anomaly as the quaternionic system of vector analysis. I have examined a good deal of his paper, and can find nothing quaternionic about it except the language concerned in his symbols. On conversion to purely vectorial form, I find that it is greatly improved. I would suggest that he give up the quaternion. If he does not like my notation, or Prof. Gibbs's, or Prof. Macfarlane's, and will invent one for himself, it will receive proper consideration. He will greatly extend the sphere of his usefulness by the conversion. A difficulty in the way is that he has got used to quaternions. I know what it is, as I was in the quaternionic slough myself once. But I made an effort, and recovered my self, and have little doubt that Prof. MacAulay can do the same. Passing to Prof. Tait's letter, it seems to be very significant. The quaternionic calm and peace have been disturbed. There is confusion in the quaternionic citadel; alarms and excursions, and hurling of stones and pouring of boiling water upon the invading host. What else is the meaning of his letter, and more especially of the concluding paragraph? But the worm may turn; and turn the tables.

It would appear that Prof. Tait, being unable to bring his massive intellect to understand my vectors, or Gibbs's, or Macfarlane's, has delegated to Prof. Knott the task of examining them, apparently just upon the remote chance that there

might possibly be something in them that was not attery despicable. Prof. Knott has examined them, and has male some remarkable discoveries. One of them is that those vei methods in which the quaternion is not the master led formula of the most prodigious and alarming complexity He has counted up the number of symbols in certain equatiota Admirable critic!

Now, since this discovery, and Prof. Tait's remarks, are cal culated to discourage learners, I beg leave to say, distinely and emphatically, that there is no foundation for the imputation. Prof. Knott seems to have found a mare's nest of the b magnitude; unless, indeed, he is a practical joker, and has bees hoaxing his venerated friend. Speaking from a personal know ledge of the quaternionic formula of mathematical physics ! of the corresponding formule in my notation and in Proi Gibbs's, I can say definitely that there is very little to cho between them, so far as mere length goes. Perhaps Prof. Ko has been counting the symbols in a Cartesian formula, or in a semi cartesian one, or some kind of expanded form. I do toc write for experts who delight in the most condensed symbols I do not even claim to be an expert myself. I have to make me readers, and therefore frequently, of set purpose, give expanded forms rather than the most condensed.

But so far as regards the brief vector formule, I find that the advantage is actually in my favour. I attach no importance to this, but state it merely as a fact which upsets Profs. Knott and and Tait's conclusions. It is desirable that I should point out the reason, otherwise the fact may not be believed. In common algebra there is but one kind of product of a pair of quantities say F and 2, which is denoted by Fv. In vector algebra there are two kinds of products. One of these closely resembles tre usual product, whilst the other is widely different, being a vector itself. Accordingly, to harmonise with common algebra. I denote the scalar product by Pv. It degenerates to Fo when the vectors have the same direction. Now, since the quaternionists denote this function by - SPV, which is double as long, whilst Fv becomes SPV, it is clear that there must be an appreciable saving of space from this cause alone, because the scalar product is usually the most frequently occurring function.

But there are other causes. The quaternionic ways of specialising formulæ are sometimes both hard to read and lengthy in execution. Look at S. UaUpS. UẞUp, which I see in Tait's book. I denote this by (ap) (BP), or else by a1P1 BP1. Tait is twice as long. But the mere shortness is not important. It is distinctness that should be aimed at, and that is also secured by departing from quaternionic usage. Examples of shortening and clarifying by adopting my notation may be found on nearly every page of Tait's book.

The

Consider, for example, rotations. Quaternionists, I believe. rather pride themselves upon their power of representing a rotation by means of a quaternion. Thus, bay. continued product of a quaternion y, a vector a, and another quaternion q, produces a vector b, which is a turned round a certain axis through a certain angle. It is striking that should turn out so; but is it not also a very clumsy way of representing a rotation, to have to use two quaternions, one to pull and the other to push, in order to turn round the vector lodged between them? Is it not plainer to say bra where r is the rotator? Then we shall have acarreare=&c., if' is the reciprocal of r. Then Prof. Tait's Vgaq g¢ (g ̃by) y”) is represented by Vraror'b. See his treatise, p. 326, 3rd edition, and note how badly the q() q1 system works out there and in the neighbouring pages.

What, then, is this rotator? It is simply a linear operator, like . It is, however, of a special kind, since its conjugate and its reciprocal are one, thus =1, or = Far he it from me to follow Prof. Tait's example (see his letter) and impute to him an "imperfect assimilation" of the linear and vector operator. What I should prefer to suggest is that his admiration for the quaternionic mantle is so extreme that he will wear it in preference to a better-fitting and neater garment. If we like we can express the rotator in terms of a quaternion, in another way than above, though involving direct operations only. But I am here merely illustrating the clumsiness of the quaternionic formulæ in physical investigations, and their un. naturalness, by way of emphasising my denial and disproof of the charge made by Prof. Tait against vectorial methods. The general anti-quaternionic question I have considered elsewhere. Paignton, Devon, March 24. OLIVER HEAVISIDE.

Severe Frost at Hongkong.

THE occurrence of severe frost at moderate elevations within the Tropics must be rare. It seems worth while therefore to place on record in the columns of NATURE some portion at least of an official report on the low temperature which (as was stated in NATURE last week) occurred at Hongkong between the 15th and 18th of January:

Botanic Gardens, Hongkong, February 4, 1893. SIR,-The unprecedented cold weather which the region about Hongkong was recently subjected to calls for some notice by this department. Records of experiences of meteorological phenomena such as we have just had besides being of passing interest are so frequently of use in practical dealings with various subjects that for this reason opportunities to record unusual phenomena should not be neglected. It does not, however, come within the province of this department to go much further into the meteorological aspects of the subject than is demanded in connection with its injurious effects on vegetation.

(2) After a period of ordinary Hongkong dry, cool weather rain fell on January 13, and continued daily up to the 16th instant. In the gardens, at 300 feet above sea level, the following quantities of rain were registered with a Glaisher's rain gauge:

(3) On the 15th instant the temperature fell in the afternoon to 39° F., at 350 feet above sea level. On the 16th, at 9 a.m., it stood at 35°. On the 17th the thermometer stood at 31 at 9 a.m., which was the lowest temperature observed at the Gardens. During this period the sky was overcast except for a short time about noon on the 17th, but on the morning of the 18th it was clear and the sun shone brightly throughout the day, the temperature having risen to 43 at 4 p.m.

(4) Unfortunately there are no official records of temperature at Victoria Peak, 1818 feet above sea level, but, by such information as could be obtained from private observers in the hill district and observations made here, it seems that the temperature must have fallen at the summit to about 25° or 24° F.

(5) On the river at Canton, and between this port and that place, low temperatures were recorded in the reports of the steamships Powan and Honam. They gave

January 16 at

33

I A. M. 23° about 28 miles below Canton. at 10 A. M. 26° about 25 miles from Hongkong. at I P.M. 25 at Canton.

18 at 10 A.M. 28° about 25 miles from Hongkong.

I am indebted to the Office of the Hongkong, Canton, and Macao Steamboat Company for these returns.

(6) On the peninsula of Kowloon the cold appears to have been greater than in Hongkong; ice was seen on pools of water in the roads within fifty feet of sea-level, and at the Kowloon Docks ice was observed at the bottom, thirty feet below sealevel, of an empty dock.

(7) In the harbour the rigging of ships was coated with ice. (8) Since the records began in 1884 the temperature has not fallen, until now, at the observatory, below 40° F. I remember on one occasion, I think about seventeen years ago, ice was found at Victoria Peak, but there is no record within my experience, which extends back nearly twenty-two years, when ice was observed below 1700 feet altitude.

(9) The continued low temperature combined with fall of rain from an apparently warmer stratum of air above, resulted in the formation of ice varying in quantity from a thin coating on the upper leaves of pine trees growing at 300 feet above sea level, to a thick encasement of perfectly transparent solid ice of 51 inches in circumference on the blades and bents of grass at the summit of Victoria Peak. The grass bents themselves, which were the foundation on which the ice accumulated, were not more than an eighth of an inch in diameter, yet the formation of ice was so gradual that with the enormous accumulation of ice, which became its own support, the bents retained their natural upright, or but slightly pendent position. These large accumulations of ice were on the windward side of the hill where rain

drifted, but even on the lee side the average coating of ice was about 3 inches in circumference.

(10) Evergreen shrubs and trees carried on their leaves solid coverings of ice of an inch in thickness. The great weight of this ice caused the branches of trees to assume a pendent form, the strain in many cases causing the limbs to snap off with a crash. All vegetation throughout the hill regions of the Colony was thus covered with ice, as were also most other objects. Telegraph and telephone wires from Victoria Gap upwards were covered with ice of an inch in thickness, and, in addition, carried icicles as much as three inches in length as close as they could be packed side by side. This caused many of the telephone wires to break, and the iron post at Victoria Gap which supported them was snapped off a few inches above the ground.

(1) The windward sides of the walls of the look-out house at the Peak were from top to bottom covered with perfectly trans parent ice of an inch in thickness.

(12) All the hills on the mainland and Lantao island were likewise white with ice, one of the hills (3147 feet) of Lantao having what appeared to be snow for some few hundreds of feet down from its summit. As early as the evening of January 15 the summit of Taimoshan (about 3300 feet) on the mainland had assumed a whitish appearance, presumably from ice or

(15) The damage in the gardens consist chiefly in the injury or destruction of leaves, but some plants are quite killed, these being natives of much warmer regions than Hongkong. Many of the decorative plants which were not killed will be months before they can regain their ornamental appearance.

(16) Every possible precaution was adopted to minimise the effect of the cold. The plant-houses, which are provided with screens merely to produce shade, were all matted in and the roofs covered with straw. In spite of these precautions, however, many plants suffered very severely. Of ferns in the houses Polypodium Heracleum and Adiantum tetradactylon suffered most, other kinds being but little affected.

(17) In the orchid-house, which was covered with mats and straw, all our best orchids have suffered very greatly, many being entirely killed while others were so much injured that, even if they survive, it may be some years before they regain their previous luxuriant state. A healthy plant, received from Calcutta several years ago, of Dendrobium aggregatum, is apparently killed, while plants of the same species growing by its side, and also others on trees where they had no shelter, which I collected ten years ago on the Lo-fau mountains, about sixty miles from Canton, have escaped unharmed. This seems to show the capability of the plant in adapting itself to colder regions than it is generally found in.

(19) The highest point of the Gardens is 320 feet above sealevel, the lowest part 175 feet. Some plants of the same kinds which were damaged at the upper portions were uninjured at the lower parts of the Gardens.

(20) Of exotic trees planted on the hills Albizzia Lebbek, Aleurites triloba (candle-nut-tree) and Eugenia Jambos (the rose-apple-tree) had all their leaves killed at and upwards of 600 feet above sea level. Trees of the rose-apple at about 800 feet altitude have been entirely killed.

(21) At 600 feet altitude indigenous plants began to be affected, the injuries increasing with higher altitude until at about 900 feet when the extreme limit of low temperature which some plants could bear was reached, and death ensued. Most of these are tropical plants of which Hongkong, Formosa, the Luchu Islands in the Far East, and Sikkim and Himalaya in India are the northern limits of the geographical area from which they have been recorded. Of the plants killed or injured, Ficus Harlandi, Benth., Gordonia anomala, Spreng., and Garcinia oblongifolia, Champ, are known only from Hongkong. Although many of our indigenous plants have not been yet discovered elsewhere, it is to be expected that when China is better known they will be found over a larger area than the restricted one of this island. The fact of the above named plants having succumbed to the late frost indicates that when they are discovered elsewhere they will be found southward of Hongkong.

(22) Considerable damage to vegetation seems to have been caused about Canton, where the alluvial lands are highly culti

vated. The Rev. Dr. B. C. Henry, in a letter dated January 26, informs me that "the destruction of vegetation about Canton has been very great. The banana plantations are ruined, and the bamboos have suffered. The Aleurites triloba look all shrivelled up, while Begonias, Euphorbias, Crotons and scores of others are simply destroyed." What Dr. Henry reports indicates severer weather at Canton than here, Aleurites triloba leaves being shrivelled up at Canton, while they are here at 300 feet altitude uninjured, but at 600 feet they are affected, and completely destroyed a little higher up the hill.

(23) Accompanying this report are six photographic views which were taken on January 16 showing the ice at various places in the Peak district. It is somewhat difficult to represent ice in photographs, as bright light has much the same effect as ice which owes its white appearance merely to reflected light, but it will be understood that the white in these views is produced by ice. CHARLES FORD,

Superintendent Botanical and Afforestation Department. HON. G. T. M. O'BRIEN. C. M. G.,

Colonial Secretary, &c.

The importance of such facts as these in connection with geographical distribution can hardly be overrated. It is customary to compare the range of a plant with the corresponding mean annual temperature. But it is obvious that the exterminating effect of occasional low temperature must override every other condition. An island is often the last refuge of a species not found elsewhere. Such a frost as occurred in Hongkong would erase the Double Cocoa-nut in all probability from the face of creation, if it occurred in the Seychelles. In any case islands are not easily restocked except with littoral vegetations and the trees distributed by carpophagous birds. It seems evident therefore that the geographical distribution of plants may still be influenced by causes which are catastrophic in their nature. Of this, although not from cold, there is already a striking illustration in the simultaneous destruction of the entire forest vegetation which at one time covered the island of Trinidad in the South Atlantic. Mr. Knight, in the account which he has given in the "Cruise of the Falcon," conjectures that the cause was more probably volcanic than a long drought.

The wave of cold which affected Hongkong (or at any rate the atmospheric conditions which produced it) seems to have been tolerably extended in its range. My friend, Dr. Trimen, writes to me on February 6 from Ceylon :

"We are having a wonderfully fine and dry time here, with extraordinary cold mornings. Here at Pecadeniya we have been registering at 6 a.m. 53° and 54° F., the lowest ever previ. ously known being a little below 60°. The middle of the day is very hot. Hakgala has been getting frost for the first time on record."

He does not give any dates; but the two exceptional circumstances are sufficiently near together to make it probable that some common cause produced them both.

Royal Gardens, Kew, March 28.

W. T. THISELTON-DYER.

P.S. Since writing the above I have received from the Colonial Office the accompanying report on the weather of January from the Hongkong Observatory.-[W. T. T.-D.]

The mean temperature was below the average from the 14th to the 24th. The coldest day (air 35° 2, damp bulb 32°8) was the 16th. The lowest mean temperature of the damp-bulb thermometer occurred on the 17th (air 36°2, damp bulb 30°·9). Circumstances were anti-cyclonic, with probably abnormally slight decrease of temperature with height. Snow-storms were reported from China to the north and east of the colony. From Macao snow was reported, but that appears to have really consisted of small-sized hail, which fell for four hours. Neither snow nor hail were seen in Hongkong, but the tops of the hills appeared to be covered by snow or hoar-frost. Water exposed in buckets or in pools was several mornings found covered with ice about inch thick, and a few hundred feet above sea-level both the grass and branches of trees, being cooled below the temperature of the air (which did not fall below freezing-point) owing to evaporation and radiation, were encased in unusually clear and transparent ice without any appearance of crystallisation. As far south as the Straits Settlements the cold was felt, but in a less degree. The temperature appears not to have fallen below 70° in Singapore. At sea strong northerly breezes were

observed during the greatest cold. The colony was sheltered by the mainland, and only light northerly breezes were registered till the 20th, when the wind backed to west. It veered to east on the 21st. During the coldest days the pressure was from one to two-tenths of an inch of mercury above the mean. The sky was overcast, but cleared on the evening of the 17th. Owing to radiation the extreme temperatures occurred after this epoch the lowest air-temperature 32°o about 7 a. m. on the 18th, and the lowest damp-bulb temperature 27°7 about 2.30 a. m. on the same day. W. DOBERCK, Director Hongkong Observatory, February 1.

Mr. Preece on Lightning Protection.

IN the recent Presidential Address to the Institution of Electrical Engineers by Mr. Preece, I find the following reference to myself.

"Prof. Oliver Lodge has... endeavoured to modify ou views as to the behaviour of lightning discharges, and as to the form of protectors, but without much success. His views have not received general acceptance, for they are contrary to fac and to experience.'

that the general and semi-scientific public are apt to take Mr I was quite prepared to laugh at this with the rest, but I fini Preece's little jokes, of which there are many towards the ead of this address, as serious and authoritative statements of

scientific fact. And it has been represented to me that unless take some notice of the above, it may be assumed that I wish silently to withdraw from an untenable position without ac knowledging having made a mistake.

Indeed, I have already been questioned by a scientific worker as to whether I accepted the above statement as in any sense corresponding to truth.

My reply is that so far was I from that attitude, that I did not suppose that the statement was either meant or would e taken seriously.

The broad question of scientific fact is this:-Given a electrostatic charge at high potential, can the potential be reduced to zero most quietly and safely by a good conductor by a bad one?

The old lightning-rod doctrine (or drain-pipe theory) said, by an extravagantly good one. I say, by a reasonably bad one. I you employ too good a conductor the mean square of current is appallingly strong, and all manner of dangerous oscillations are set up; whereas in a bad conductor the discharge can be more nearly dead-beat. These oscillations have been experimentally and mathematically demonstrated in a great variety of ways, the unexpected and distinct effects they are able to produce have been displayed, and Messrs. Whittaker have published for më a large book about them.

Some critics have sensibly objected that the book is too big, but I am not aware of any scientific authority who controvert my position.

If Mr. Preece only means that these views regarding lightning and its dangers are not yet practically accepted by the grea British Telegraphic Department, that is, I admit, perfectly tree OLIVER LODGE.

The Author of the Word "Eudiometer." FOR Some time past I have been endeavouring to find out the originator of the name eudiometer, which is now applied to the measuring tubes used in gas analysis, and possibly the result of the search may be of interest to some of the readers of NATURE Naturally my first resort was to text-books and dictionaries but although the derivation of the word is sometimes given, the name of the author is not stated.

I had great hopes that the third edition of the "Encyclopedia Britannica," published in 1797, would contain the desired infor mation, for the article "Eudiometer" must have been written not long after the invention of the instrument, but it merely calls an instrument for observing the purity of the atmospherica air." Descriptions of many forms of eudiometer follow.

The New English Dictionary gives the derivation and the first quotation is "1777. De Magellan (title), Glass apparate for making mineral waters...... with the description of some pe Eudiometers"; another is " 1807. Pepys. Eudiometer in Pu