RURAL ENGINEERING. 189 



The conclusions drawn from tlie test are as folJows: The flash process of 

 pasteurization requires approximately 17 per cent more heat than the holder 

 process and there is a correspondingly wider range through which the milk or 

 cream must be cooled. The proper design and arrangement of the heater, re- 

 generator, cooler, piping, and refrigerating apparatus have much to do with the 

 etliiient operation of the plant. With poorly arranged apparatus and leaky 

 piping the loss in heat may reach approximately 30 per cent of that required to 

 pasteurize, which it is practicable to reduce to a negligible amount. It is prac- 

 ticable to use exhaust steam from the engine and steam-driven auxiliaries, or 

 water heated by exhaust steam, to furnish heat with which to pasteurize both 

 milk and cream. Usually there is sufficient heat in the exhaust steam which 

 is allowed to waste in milk plants and creameries to do the pasteurizing. For 

 every 400 lbs. of milk pasteurized per hour with exhaust steam, approximately 

 (■ne horsepower is taken oft the boiler plant. 



Electric stimulation of plant growth, W. D. Peaslee {Jour. Electricity, 32 

 (1914), ^0. 4, pp. 69-72, figs. S).— Studies of stimulation of plant growth by 

 electrical methods are reported. 



A direct current passing through the soil containing the seeds or roots of plants 

 caused a gain in root structure, and the electrified plants after transplanting 

 wei-e more hardy and grew faster than the nonelectrified. Similar tests with 

 alternating currents gave positive results only at very low power values. 



The application of a voltage stress to the atmosphere around plants caused 

 good results only when the stress was api)lied on cloudy days and at night. Two 

 important points brought out are (1) that no difference in stimulative effect was 

 found when using the ground as positive or negative, and (2) that there is some 

 tendency to show for all plants a curve approximating a straight line within 

 certain limits, the slope of this curve being different for each plant. Practi- 

 cally the same results were secured when using a Tesla coil as when using a 

 Wimshurst machine. 



It is concluded in general that indirect stimulation of the root or plant in- 

 creases the functional activity of the organs if they are far enough from the 

 point of application of the stimulus to avoid the effect of direct stimulation. 

 Though the immediate effect of direct stimulation is to retard growth, it in- 

 creases the internal energy of the plant and the after effect is to increase the 

 growth rate. Plants are very sensitive to fatigue and the stimulation must be 

 of such degree and duration that fatigue is avoided if the net result of the 

 treatment is to be beneficial. 



The dissolving of zinc from pure zinc and galvanized iron pipes by water 

 supplies, Ki. B. Lehmann {Jotir. Gasbeleucht., 56 {1913), pp. 111-122; abs. in- 

 Wasser u. AMoasser, 7 {1914), No. 10, pp. 423, 4'^4)- — Investigations by the 

 author and. others on the action of both hard and soft water on galvanized and 

 pure zinc water pipes show that under the best conditions the zinc content of the 

 water was always moderate, and greater amounts were obtained from the gal- 

 vanized than from the pure zinc pipes as long as zinc remained on the galva- 

 nized pipe. It is concluded that the use of pure zinc water pipe is hygienic 

 and unobjectionable. 



The hot water supply plant for private houses, C. A. Gullino {Gsndhts. 

 Ingen., 31 {1914), No. 2, pp. 24-28, figs. 6). — The author discusses in detail the 

 design of private hot water supply plants for both city and farm houses, econ- 

 omy and efficiency being the chief considerations. 



Elements of heating, B. N. Irwin {Power, 39 {1914), No. 3, pp. 89-92).— 

 This article gives practical information regarding air, steam, and water as 

 media for the distribution of heat, including tables of data for computing 

 the heat losses from a building and the radiating surface required. 



