expense, usually of brick or stone, and the protection to the ice consists in air spaces, or in dry, light vegetable substances inclosed between two walls. In this vicinity, on the borders of the lakes, where ice is least valuable, they are usually built of wood, in which case they are of two walls, formed by placing two ranges of joist upright, framed into plates at the top, and placed in the ground at the bottom, or framed into sills; these two ranges are ceiled with boards secured to that side of each range which is nearest the other, and the space between the two boardings filled with refuse tan, wet from the yards. This wet tan is frozen during the winter, and until it is thawed in the spring and summer, little waste occurs; afterward the waste is more rapid, but as a large portion of the ice is shipped or otherwise used before this takes place, the loss in quantity is small, and, occurring before the expenses of transportation have been paid, is of less pecuniary moment.

In one instance, brick has been used in the construction of an icehouse which covers 36,000 feet of land, and the vaults of the ice-house are forty feet in depth, and its walls are four feet thick from outside to inside, inclosing two sets of air-spaces. Such a construction is more costly, but has the advantage of durability and safety from fire, to which ice-houses are much exposed from the frequent juxtaposition of railroad engines, and the light, dry, materials used about them to cover and otherwise preserve ice.

In the winter of 1847 about $650 were paid daily for the labor of men, and $230 for that of horses, when the weather was most favorable for cutting ice. Such activity is, however, of short duration, as there are not generally more than twenty days in a season which are really favorable to the operation of securing ice. The price paid is usually one dollar per day for horses and men.

At first, the implements of husbandry only were used in securing ice, but as the trade became more important, other machines and different methods were adopted, and abandoned when better were brought forward or when the increased magnitude of the business required greater facilities. More ice is now secured in one favorable day than would have supplied the whole trade in 1832. Ordinarily, before there has been cold enough to form ice of suitable thickness, snow falls on its surface. If this occurs when the ice is four or more inches in thickness, and the snow not heavy enough to sink the ice, it can be removed by using horses attached to the " snow scraper" and under such circumstances this is the method in common use. But if snow falls so heavy as to bring the water above the surface of the ice, it is removed, after it has congealed into snow-ice, with the "ice-plane," which takes off about two inches deep and twenty two wide, of its surface. This machine is drawn by two horses, and is guided by inserting its "guides" into grooves previously made with the "ice cutter." The chips made by it are scraped off in the same manner as dry snow. These preliminary expenses are often very great; frequently, after much expense has been incurred to remove a body of snow or snow ice, the weather be comes warm and spoils the ice on which so much has been expended. And, on the other hand, if it is not done and the cold continues, there will be little or no increase of thickness to the ice, which is equally a disaster.

།

When ice has been formed of sufficient thickness, and freed from snow and snow-ice, it is reduced to blocks of uniform size, ordinarily 22 inches square, by the "ice-cutter." This machine is similar to a carpenter's plough, except that it has a series of cutting chisels, one succeeding another, and deepening the groove. It is drawn by a horse, and cuts at one passage about two inches deep, and if the ice requires to be planed to remove snow-ice, the guides of the "snow-plane" are used in grooves of this depth, but when grooves are required to split from, the ice-cutter" should be drawn two or three times through each. These grooves should be parallel to each other and, to make them so, the "ice-cutter" has a guide, which is placed in the last groove made. When the grooves in one direction have been made, others at right angles with them are produced in the same manner. After this has been done, one groove at the end is opened, and also the two outside grooves; a wedging bar is then stricken into the groove next the end one, and at several places along its length, which detaches it easily from the mass; then the same bar is forced, with a slight blow, into the transverse grooves, which reduces the ice to very uniform square blocks. The blocks of ice thus formed are brought to the receiving doors of the ice-houses, (which are built on the immediate borders of the ponds,) either by placing them on sleds, or floating in canals cut through the ice. Various modes of elevating the ice are in use; the endless chain, in combination with the inclined plane, has been successfully used, and also the common pile driving steam engine; but at present, horse-power is more used than any other. The ice is placed in the houses in regular courses, every block exactly covering the next below it. When a vault has been filled, it is immediately covered with wood shavings and the receiving doors fitted up, to prevent waste, until the contents are required for shipment abroad or use at home.

The weight of ice for shipment is usually determined at the wharves, immediately before being put on shipboard, on scales which have been constructed for the purpose; and this single operation settles the weight to be paid for by the party for whose account the ice is shipped, the amount due for freight on shipboard, for transportation on the railroad, and that which is to be received by the owner of the ice.

The following Returns will show the growing importance of this trade to Boston.

THE LAWS OF MORTALITY.

From the Encyclopædia Americana.

The increased attention which is now given to the subject of Life Insurance, throughout this country, has induced us to republish the following condensed articles from the Encyclopædia Americana and from the British and Foreign Medico-Chirurgical Review for 1848. Within the last two years the number of Life Insurance Companies in the U. S. has been doubled; added to these are numerous Health Insurance Companies, all of which have in view a general benefit to society at large by insurance against the evils arising from the loss of life and loss of health. The new facts now stated, will be interesting to all parties.-(ED. B. M.)

The extreme limit of human life, and the means of attaining it, have been a subject of general interest, both in ancient and modern times, and the physiologist and political economist are alike attracted by the inquiry. It is for the student of biblical antiquities to decide in what sense we are to understand the word year in the scriptural accounts of the antediluvians; whether it signifies a revolution of the sun or of the moon, or whether their extreme longevity is only the creation of tradition. In the sense which we now give to the word year, the accounts would make the constitution of men at the period referred to, very different from what it is at present, or has been, at any period from which observations on the duration of human life have been transmitted to us. The results of all these observations, in regard to the length of life in given circumstances, do not essentially differ. Pliny affords some valuable statistical information, if accurate, regarding the period at which he lived, obtained from an official, and, apparently, authentic source, the census, directed by the emperor Vespasian, in the year 76 of the Christian era. From this we learn that, at the time of the computation, there were, in the part of Italy comprised between the Appennines and the Po, 124 individuals aged 100 years and upwards, viz. 54 of 100 years, 57 of 110,2 of 125, 4 of 130, 4 of 135 to 137, and 3 of 140. At Parma, a man was living aged 120, and 2 aged 130; at Faenza, a female aged 132; and at a small town near Placentia, called Velleiacium, lived 6 persons aged 110 years each, and 4 of 120. These estimates, however, do not accord with those of Ulpian, who seems to have taken especial care to become acquainted with the facts of the case. His researches prove that the expectation of life in Rome, at that time, was much less than it now is in London, or in any of our cities. Hufeland, indeed, in his Macrobiotics, asserts that the tables of Ulpian agree perfectly with those afforded by the great cities of Europe, and that they exhibit the probabilities of life in ancient Rome to have been the same as those of modern London. But Doctor F. Bisset Hawkins, in his Elements of Medical Statistics (London, 1829), says that the tables, kept by the censors for 1000 years, and constituting registers of population, sex, age, disease, &c., according to Ulpian (who was a lawyer, and a minister of Alexander Severus), refer only to free citizens, and that, to draw a just comparison between Rome and London, it would be necessary to take, among the inhabitants of the latter city, only those who were similarly circumstanced, viz: those whose condition is easy; in which case, the balance would be greatly in favor of modern times.

Mr. Finlayson has ascertained, from very extensive observation on the decrement of life prevailing among the nominees of the Tontines, and other life annuities, granted by the authority of parliament, during the last 40 years, that the expectation of life is above 50 years for persons thus situated, which affords the easy classes of England a superiority of 20 years above even the easy classes among the Romans. The mean term of life among the easy classes of Paris is, at present, 42 years, which gives them an advantage of 12 years above the Romans. In the third century of the Christian era, the expectation of life in Rome was as follows: From birth to 20, there was a probability of 30 years; from 20 to 25, of 28 years; from 25 to 30, 25 years; from 30 to 35, 22 years; from 35 to 40, 20 years; from 40 to 45, 18 years; from 45 to 50, 13 years; from 50 to 55, 9 years; from 55 to 60, 7 years; from 60 to 65, 5 years. Farther than this the computation did not extend. The census taken from time to time in England affords us information of an unquestionable character. The first actual enumeration of the inhabitants was made in 1801, and gave an annual mortality of 1 in 44.8. The third and last census was made in 1821, and showed a mortality of 1 to 58. (See Abstract of the Answers and Returns made pursuant to an Act passed in the Year of George IV, &c., by Rickman.) The mortality then had decreased considerably within 20 years. In France, the annual deaths were, in 1781, 1 in 20; in 1802, 1 in 30; in 1823, 1 in 40. In the Pays de Vaud, the mortality is 1 to 49; in Sweden and Holland, 1 to 48; in Russia, 1 to 41; in Austria, 1 to 38. Wherever records have been kept, we find that mortality has decreased with civilization. Perhaps a few more persons reach extreme old age among nations in a state of little cultivation; but it is certain that more children die, and the chance of life, in general, is much less. In Geneva, records of mortality have been kept since 1530, which show that a child born there has, at present, five times greater expectation of life than one born three centuries ago. A like improvement has taken place in the salubrity of large towns. The annual mortality of London, in 1700, was 1 in 25; in 1751, 1 in 21; in 1801, and the 4 years preceding, 1 in 35; in 1811, 1 in 38; and in 1821, 1 in 40; the value of life having thus doubled, in London, within the last 80 years. In Paris, about the middle of the last century, the mortality was 1 in 25; at present, it is about 1 in 32; and it has been calculated that, in the fourteenth century, it was one in 16 or 17. The annual mortality in Berlin has decreased during the last 50 or 60 years, from 1 in 28 to 1 in 34. The mortality in Manchester was, about the middle of the last century, 1 in 25; in 1770, 1 in 28; 40 years afterwards, in 1811, the annual deaths were diminished to 1 in 44; and, in 1821, they seem to have been still fewer. In the middle of the last century, the mortality of Vienna was 1 in 20; it has not, however, improved in the same proportion as some of the other European cities. According to recent calculation, it is, even now, 1 in 221, or about twice the proportion of Philadelphia, Manchester or Glasgow. Many years ago, Mr. Finlayson drew up the following table, to exhibit the difference in the value of life, at two periods of the seventeenth and eighteenth centuries. Had it been calculated for 1830, the results would have been still more remarkable.

The following is the annual mortality of some of the chief cities of Europe and this country:

From Dec. 12, 1828, to Dec. 15, 1829, in London, the whole number of deaths was 23,525. The proportion of deaths, in different ages, was

Thirty and forty,

Forty and fifty,

2094

2153

1843

749

95

On the average of eight years, from 1807 to 1814 inclusive, there died annually within the city of Philadelphia and the Liberties, the following proportion of persons, of different ages, compared with the total number of deaths:

Ten to twenty,

Twenty to thirty,

Thirty to forty,

10-99 One hundred to one hundred & ten, 0-0009

Another question of interest is the inquiry in what degree the various trades and professions are favorable to human life, or the contrary. Several statements have lately been published respecting this subject, but farther and more copious observations are required, to afford satisfactory results. The Literary Gazette gives, in a tabular form, the results of a work on this subject, from the pen of Mr. Thackrah, an