of the porous cup, more water is drawn up through the capillary arm to take its place. The amount evaporated in a given time is read off directly from the water level in the graduated arm.

This instrument is useful in measuring the relative drying effects of air at various temperatures, humidities and rates of air movement. It should be borne in mind that the absolute quantity of water evaporated is, of course, dependent on the size, shape and material of the porous cup and of its temperature.

Each cup is standardized by the makers against a cup in their possession and the product of the amount of water evaporated from any cup and its coefficient gives results comparable for all cups.

This cup

has been used by horticulturists in studying the effect of dryness and moisture on plant growth and its use is described in a paper entitled, "Atmometry and the Porous Cup Atmometer," by B. E. Livingston This paper and the cup may be secured from The Plant World, Tucson, Arizona The particular U-tube connection shown in

the photograph was devised by the New York State Commission on Ventilation and is used in studying dryness as related to ventilation.

THE KATA-THERMOMETER.

This instrument measures the combined effect of the three methods by which air extracts heat from a hot object-radiation, convection and evaporation. It consists of two glass bulbs, shaped as in the photograph, and filled with a colored spirit. The necks of the bulb are graduated in degrees Fahrenheit from 95 to 100. The bulbs are placed in hot water until the spirit column rises well above the 100° mark. The bulb without the cloth covering is then dried and either placed in the rack provided or suspended in the air on a string. The bulb with the cloth covering is gently shaken to remove excess water and then exposed similarly to the dry bulb.

Both bulbs lose heat to the surrounding air and their rate of losing heat is measured by timing the spirit column in its fall from 100° to 95° F. Each bulb possesses a coefficient which is divided by the time of fall in seconds and the quotients thus obtained, when added together, express the heatextractive power of the air in terms of calories per square centimeter per second.

The kata-thermometer is useful in measuring the deheating effect of the atmosphere during the time the reading is being made. It is not possible with this instrument, however, to follow the slight fluctuations in deheating effect which are constantly occurring. Prof. Phelps, of the New York State Commission on Ventilation, has attempted to meet this situation with a wet-bulb thermometer to which a constant amount of heat is supplied through an electrically-heated coil. If the heat production is constant then any change in the rate of heat loss must show itself in the actual temperature of the instrument. If the air temperature and relative humidity are high and the air movement is slight. the rate of heat loss from the heated bulb will be slow and, inasmuch as the amount of heat supplied does not change, the mercury column on the thermometer will rise up to a point where its rate of heat supply and heat loss is balanced. Heat is thus being stored up in the instrument.

In a cold atmosphere heat is taken away from the bulb about as quickly as received and the mercury column does not get an Opportunity to rise. The fluctuations in ate of heat loss may then be determined y reading the mercury column at interals or by fitting up a bulb on a recording

psychrometer and thus obtaining a continuous inked record of the heat loss changes.

This type of instrument has been named the "Comfortmeter" as it measures, in a way, the degree of comfort which air produces. It is the rate of heat loss from all causes that determines body comfort and this instrument as does the kata-thermometer, measures not merely the temperature of the air alone, not merely its relative humidity, not merely the velocity and constancy of air movement, but the combined effect of all three.

Two forms of the "Comfortmeter" have been used by the Ventilation Commission in its work. This instrument, however, is in an early stage of development and any further details of construction are without special interest at this time. The significance of the readings and the form of scales used must also await further experience for interpretation. The kata-thermometer was designed by Dr. Leonard Hill, of London. It is manufactured and sold in this country by the Fiebe-Gorman Co., Monadnock Block, Chicago, Ill.

Publicity for the Heating Engineer.

Under the title of "Simple Plan for Dehydrating Food is Discovered by Engineer," the New York Globe, in its issue of July 26, featured the drying session of The American Society of Heating and Ventilating Engineers, at its recent meeting in Chicago, lays special emphasis on the suggestion made by Walter L. Fleisher, of New York, at that meeting, that the heating and ventilating plants in public school buildings be utilized, during the summer months, for drying fruits and vegetables. The article is written by Alfred W. McCann, the well-known food expert. The article, in part, is as follows: Walter L. Fleisher, a "heating and ventilating engineer" of New York City, is the father of an idea which promises, if acted upon by the fathers of the government at Washington and the various state and city fathers who dwell in every voting centre of the United States, to revolutionize the canned food industry.

Walter Fleisher is a member of The American Society of Heating and Ventilating Engineers. It was at a meeting of this Association at the La Salle Hotel, Chicago, recently that he justified his existence for all time by proposing an idea so simple, and yet so rich in possibilities, that it

promises to upset all the existing notions on the subject.

Fleisher for three or four months has been doing experimental work in dehydration for the Westchester Association, now operating some dehydrators at White Plains, the mayor's committee and the Department of Agriculture. Like all other engineers honestly interested in their work, he has found that there is really nothing new either in the methods or in the products, and has said it so bluntly and sincerely.

"The main trouble with the whole proposition," said Fleisher to his fellow engineers, "has been that we have never attempted to use the apparatus and plants. already at hand. We have always been balked by the objection of cost. The thing is too expensive to be practicable, say any number of interested people.

"Yet the facts are that the things needed for a successful dehydrating plant are a large blower or fan, a steam radiator or heater to warm the air, a boiler for generating heat for the radiator, a sheet-iron tube to carry the heated air to the drier, and a method of regulating temperature, either by hand or with a thermostat.

"In every modern school building in America as well as in every modern public building, there is a modern heating and ventilating apparatus. Municipal buildings, state buildings, federal buildings, have been erected with these modern heating and ventilating plants all over the country.

"In every one of these institutions is tucked away an ideal dehydrating plant which is never used. Many of these buildings are practically shut tight during the very months of the year in which our perishable foods are marketed. I propose. that in every school conveniently located, as well as in every state or federal building of the same character, in which a modern heating and ventilating plant is now installed, some room near the source of supply of heat ought to be turned into a dehydration.

"This can be done with very small expense, and the heat, thermostatically controlled, can be brought from the fan to this drying room, and there applied for the proper dehydration of any of the fruits or vegetables which the community might have for preservation."

Mr. Fleisher stated that he would be not only willing to take any school building in New York City and design the necessary changes that would convert one of its rooms into a community dehydrating plant, but that he would enthusiastically embrace the opportunity.

CORRESPONDENCE

The Development of TemperatureControlling Apparatus.

EDITOR HEATING AND VENTILATING MAGAZINE:

Large buildings under construction are now, as a rule, equipped with an automatic heatregulating system, such as the Johnson or Powers method of compressed-air control. In old buildings, however, these compressed-air systems are rarely installed, because of the cost and inconvenience which would result from the tearing up of floors and plaster in order to lay the air pipes. Thus, the heat in these buildings is allowed to run wild, to the great discomfort of the occupants.

Can you tell me why it is that a suitable electric system of heat control has not been developed to meet this demand? I have made considerable investigation to ascertain why an electric system has not been developed and have come to the conclusion that the difficulty lies in obtaining a suitable electric valve which will perform the same functions as the rubber or metal diaphragm in the compressedair system. Can you advise me as to the correctness of my conclusion?

In an electric system, a single transformer could furnish sufficient low-voltage current from the 110-volt lighting circuit to supply the entire building. The current could be carried around the main walls by a single small pipe or conduit, over the molding in the hall, and the voltage and current could be made sufficiently low to enable the leads from the main conduit to the rooms to be laid bare and still not violate the rules of the electric code. Thus no tearing up of floors or plaster would be necessary.

There is also a big demand for an electric system in large apartment buildings. The hot water or steam piping could be so arranged that a single valve, controlled by a single thermostat within each apartment, would control the heat of that apartment. Also the radiation surface of the radiators in the most exposed apartment of the building could be made a little smaller than those of the other apartments so that if the exposed apartment obtains enough heat, the other apartments would also. A second thermostat in the exposed apartment would control the drafts of the furnace, in conjunction with the safety valves of the furnace, thus making the entire building automatically controlled.

L. R.

Our correspondent is quite correct in saying that there is a good field for automatic control in buildings already erected, and yet this field is not as large as might readily be supposed. There has never been any argument made against the desirability of automatic control of all heating devices and systems, no matter where placed or how operated, but to develop such control so as to be economical to install, positive in action and dependable at all times has not been so easy.

There is, however, a method of electrical control which has been developed by the Gold Car Heating & Lighting Co., of New York City, for use on car heating apparatus where the steam pressures run anywhere up to 100 lbs. The fact that this apparatus gives satisfactory operation under such pressures and when constantly subjected to the jolting of the car indicates its practicability. This system utilizes direct electric current, usually at 110 volts and consumes between 5 and 10 watts of current, according to the steam pressure. A similar apparatus to work on alternating current has not yet been perfected and, therefore, the voltage could not be handled by a transformer, as suggested, as a transformer will supply only A. C. current. Neither could sufficient force be obtained to operate the steam valves economically unless a voltage much higher than that suggested by our correspondent be used. In other words Underwriters' rules would have to be followed in the installation of wiring.

The electric thermostat for this system is simply a switch operating the magnet valve which consists of a solenoid which, when energized, forces the valve stem down and closes the valve. When de-energized a spring raises and holds the valve open the same as in the ordinary pneumatic system.

The original Johnson system was also electrical in so far as the thermostat was concerned, this controlling a pneumatic valve on the air line by means of a swinging armature which was turned by the energizing of adjacent magnets so as to throw the air on and off the pneumatic line. These thermostats operated such small valves that it was possible to use a current from a series of bell batteries but the danger of running out. these batteries by an accidental short circuit, the constant wearing out of the batteries from excessive operation during cold weather (thus throwing the control of the whole building out) and the trouble experienced when these batteries were neglected led to the abandonment of this system.

Another control manufacturer who does not yet make such an electrical control states that it would be entirely feasible to

EDITOR HEATING AND VENTILATING MAGAZINE:

IN THE HEATING AND VENTILATING MAGAZINE for May, (page 53), you published a reply to some questions in regard to heating by exhaust steam. At the end of this reply (bottom of first column, page 54), you give an analysis of the amount of heat subtracted from the steam in the process of passing through the steam engine.

I would respectfully call your attention to the fact that your analysis is incorrect in that you have neglected the fact that part of the heat converted into work in a steam engine is supplied by actual condensation of the steam, so that, under ordinary conditions, the exhaust steam which leaves the engine is not dry steam, but contains a certain amount of moisture. That this is true can be easily proved from your own figures. For instance, according to these figures, each pound of steam gives up 38 B. T. U. Since the engine is rated at 40 lbs. of steam per H. P. hour, this gives 1520 B. T. U. per H. P. hour furnished by the steam. Since one H. P. hour is equivalent to 2545 B. T. U., this would give the engine a mechanical efficiency of something like 170%. The answer is, of course, as stated above, that not all of the heat necessary for producing work in the engine cylinder comes from the reduction in pressure of the steam, but part of it comes from actual condensation of the steam itself. Hartford, Conn. B.

Our correspondent is quite correct, but he will note that we stated:

"On account of small losses in the engine and the possibility of slightly higher condensing ability in some parts of the system we could not recommend over 95% of the above, say 11,400 sq. ft. for cast-iron surface, or 9,500 sq. ft. for pipe coil surface."

The small losses referred to mean the condensation and radiation losses occuring in the cylinder. We were also careful to say "about 4,000 lbs. of steam would be available" as the pounds of exhaust could not quite equal the pounds of steam supplied. Actual experiment has proved that only 4% more steam is required to operate an engine, than to pass it through a reducing valve and not operate the engine, both producing thermally the same heating effect after their passage. Therefore, a thermal efficiency of 96.8 seems pretty nearly correct, for on this basis if it took 100 lbs. of steam at high pressure to do a certain heating work it would take 104 lbs. supplied to an engine to do the same heating work after passing through the engine. In the case in question, with the steam passing through the engine, say it takes 104 lbs. Then, if our thermal efficiency figure is correct, 104 X 96.8% thermal efficiency must equal the actual heating effect of the exhaust; in reality it does equal 100.672 lbs. or about as close as theoretical figures can be made to check with actual experiments.

Our correspondent has raised a most interesting question, however, regarding the B. T. U. utilized in the engine and the matter of condensation in the engine cylinder. While space limitations will not allow us to undertake a detailed discussion of engine cylinder losses we would refer our reader to a paper by David Moffatt Meyers read before The American Society of Heating and Ventilating Engineers in 1915 on the "Heating Value of Exhaust Steam." In this discussion a chart was shown covering the maximum and minimum percentage of B. T. U. contained in the initial steam supply to the engine which are also present in the exhaust. According to this chart an engine using 40 lbs. of steam per 1 H. P. would have about 94.4% to 93.8% (of the original B. T. U.) contained in the exhaust steam and ready for use in the heating system. Mr. Meyers goes on to say "It is, perhaps, hardly necessary to state that the results in the use of exhaust steam in actual practice closely agree with these determinations of heating value. Any engineer who has had the opportunity to make observations with actual measurements, has found that exhaust steam from a simple engine is worth, for heating purposes, nearly as much as live steam. I have myself been fortunate in having had opportunities for this

kind of measurement. I might mention one case where several slide valve engines were used to furnish power whose exhaust steam was absorbed by the heating system in a large manufacturing concern. The exhaust steam just balanced the heating requirements at the time of year when I made my experiment. I shut down all the engines in the plant and supplied the heating system by using the live steam at reduced pressure. The fuel was carefully weighed and it was found that just as much was consumed during the test with the engines shut down as when all the engines were developing their full quota of power. . . . I have made other tests which have checked up these results closely."

Of course, the point of cut-off has much to do with the condensation attained in the cylinder, which is only another way of saying an efficient engine makes a thermally inefficient exhaust. The longer the cut-off the less the condensation, as may be seen from steam pumps which consume only about 1% of the B. T. U. supplied, leaving their exhaust with a thermal efficiency of 99%.

Considering the fact that many engineers advocate the use of engine exhaust steam in preference to live steam and that authentic instances are known where the installation of engines has actually reduced the coal bills and perforce the pounds of steam produced we believe our reply checks very closely with the results which would be actually attained. Of course the question as originally submitted was more or less academic and hypothetical, it being impossible to exhaust an engine into a heating system at atmospheric pressureusually 3 to 10 lbs. of back pressure must be carried in such cases. It is a question, however, whether the full 4,000 lbs. of steam could not really be considered in view of the practically equal efficiency of exhaust steam found in actual practice.

Leon H. Prentice, president of the L. H. Prentice Co., Chicago, Ill., has the sympathy of his friends in the death of his wife which occurred July 30, at their home in Waukegan. It is thought her death was hastened by the drowning of her son, Hamill, about a year ago.

The New York School of Heating and Ventilating announces the opening of the fifth annual season for 1917-1918, on Monday and Wednesday evenings, commencing October 1, in Room 512, World Building, New York. Charles A. Fuller will direct the classes. The secretary is G. G. Schmidt, World Building, New York. The fee for each course (first year and second year) is $15.00.

LEGAL DECISIONS

"Accident" Under Workmen's Compensation Act.

Action was brought for compensation under the Nebraska Workmen's Compensation Act by a steam fitter's helper employed by a corporation engaged in the heating and plumbing business. The plaintiff's duty was to attend to and fire a steam-heating boiler, and he was compelled to use a narrow passageway when inspecting the steam gauges. Two iron beams lay on the boiler, and the ends projected over the passage. The plaintiff attempted to move them out of the way by pushing with his body, when he felt pain in his stomach, became faint and weak, and was compelled to cease work and be assisted home. On the third day afterwards he vomited blood, and subsequently had a slight paralytic stroke. It was held that his condition was the result of an accident as defined in section 3693 of the statute and that the inquiry arose out of and in the course of his employment. The section reads: "The word 'accident,' as used in this article shall, unless a different meaning is clearly indicated by the context, be construed to mean an unexpected or unforseen event, happening suddenly and violently, with or without human fault and producing at the time objective symptoms of an injury."-Manning vs. Pomerene, 162 N. W., 492.

Liability of School District Trustees for Heating System.

Suit was brought by a materialman who furnished a heating apparatus for a public school building in Poplar Bluff, Mo., against the members of the board of directors of the school district, based on the failure of the board to require the contractor to execute a bond to the district conditioned for the payment of all material used in the work as required by Mo. Rev. St. 1909, § 1247. That statute declares that it shall be the duty of all officials, or agents of the state or municipalities, in making contracts for public work, to require every contractor to execute a bond in an amount to be fixed by such officials, boards, commission, etc., which bond shall be conditioned for the payment of material used in such work and for labor performed. It appeared that contractors contracted to equip the school building with a heating