488 EXPERIMENT STATION EECORD. 



as a guide when contemplatiBg the purchase of an internal combustion engine 

 for farm use. The theory underlying the operation of such engines is discufwed 

 only to the extent necessary to enable one to appreciate the conditions which 

 must be met by any successful engine. The greater part of the book is devoted 

 to a discussion of the weak and strong points in the various designs, to the 

 features which give long and useful life and those which tend to cause e<irly 

 failure, and to the characteristics which best adapt different types to different 

 uses. The subject matter is presented under the following chapters : The power 

 problem; fuels; the internal combustion engine; the mechanical construction 

 of the engine; principles of operation; indicator diagrams; power and gas 

 engines; the cooling system; the valve system; comparison of two-stroke and 

 four-stroke operation ; carbureters ; electric ignition apparatus ; the governing 

 systems; lubrication; desirable and undesirable features of construction; muf- 

 fling and mufflers; power, price, and speed; and types of farm engines. 



Drive belts, their use and care, K. Krohne (Mitt. Deut. Landw. GeselL, 

 28 (1913), No. 15, pp. 225-228, figs. 7). — This article reviews much experimental 

 work with drive belts, which indicates that various kinds of work, requiring 

 various speeds and various amounts of power, require varying widths of belt and 

 pulley and diameters of pulley, with varying arrangements of pulley axle dis- 

 tances for highest power transmission. The importance is emphasized of obtain- 

 ing the proper arc of contact, especially in case of high speed drive, for which 

 purpose it is suggested that " the distance between pulley axles should be the 

 difference between pulley diameters, multiplied by 2.5." A set of curves is given 

 for determining the proper width of belt for agricultural work when the speed 

 and diameter of the smaller pulley are given. It is generally concluded that the 

 largest belt wheels possible should be chosen and that on the whole with increas- 

 ing speed belt drive becomes more satisfactory. 



The following gear ratios are suggested under the conditions named: One to 

 10 with horizontal pull by the lower part of the belt ; 1 to 8 when the belt drives 

 obliquely downward and 1 to 7 when the belt drives obliquely upward, the axle 

 distance being normal and the lower part of the belt pulling; 1 to 6 when the 

 upper part of the belt pulls, the axle distance is diminished, or the drive runs 

 more obliquely than 45° ; and from 1 to 5 to 1 to 4 maximum when there are no 

 tension-regulating devices used. The pulley width, it is stated, should be the 

 computed belt width plus 10 per cent plus 10 mm. 



Application of electric drive in greenhouses (Elect. World, 62 (1913), 

 No. 17, pp. 841-843, figs. 7). — This article deals with the use of electricity in 

 greenhouses, particularly describing the extensive use of both alternating and 

 direct current motors in a greenhouse near Chicago for operating refrigerating 

 apparatus, fertilizer unloaders and pumps, soil mixers, etc. The electrical 

 energy for this plant is supplied in part by a private generating plant, which 

 also supplies heat, and in part by a public service company. 



The mechanical preparation of cereals for seed and the influence on 

 quantity and quality of the yield, H. Wackee (Landw. Hefte, 1913, No. 21, 

 pp. 59, pi. 1, figs. 18). — This publication describes and discusses various thresh- 

 ing, cleaning, and grading machines of the latest types. It is noted that these 

 machines aid in increasing the yields of cereals by making it possible to select 

 the best seed according to absolute weight, specific weight, volume weight, size, 

 and form, and to cull out the weed seeds. 



Centrifugal cream separators, H. Todt (English Patent 15,946, July 10, 

 1913; aljs. in Jour. Soc. Chem. Indus., 32 (1913), No. 20, p. 987).— "To prevent 

 the formation of froth in the skim milk discharged from the tubes in the head 

 of the centrifugal drum, a disk is attached to the top of this head, having pas- 

 sages which form continuations of the tubes for the skim milk, the passages 



