RUEAL ENGINEERING. 891 



horsepower to determine the relative economy under different loads indicated 

 that the larger engines are as economical in the nse of fuel on a small load 

 as are the smaller engines when carrying the same load. 



Gasoline engine troubles and the care and operation of gasoline engines, 

 G. E. P. Smith {Arizona Sta. Bui. 71 {1913), pp. 797-814, pi. 1, figs. 5).— This 

 bulletin is intended primarily for the popular discussion of gasoline engine 

 troubles, but deals in addition with sevei'al other important features cncern- 

 ing the care and operation of engines. It deals particularly with 4-cycle en- 

 gines, which are said to constitute at least 95 jper cent of the gasoline engines 

 in use in Arizona. A trouble-hunting chart for gasoline engines is included 

 which takes up in detail troubles in starting and troubles after starting. 



In a discussion of fuel consumption it is pointed out that for fuel economy an 

 engine should work close up to its rated load, and that it is not advisable, there- 

 fore, to purchase an engine with much excess of power above the required 

 amount. It is further stated that the fuel consumption for a lO-horsepower 

 engine, or larger, with good conriiression should not exceed 1 pint per brake 

 horsepower hour on full rated load, or IJ pints per brake horsepower hour 

 at one-half load. 



Information obtained from investigations of Strong and Stone previously 

 noted (E. S. R., 28, p. 384) regarding the economical adjustment of the needle 

 valve is also given. 



Tests of feed mills, H. Wirth {Arb. Deut. Sek. Landeskiilt. Rat. Konigr. 

 BoJiinen, No. 19 {1914), PP- 52, figs. 13). — Seven feed mills^ including three 

 stone mills, two I'oUer mills, and two toothed disk mills, are described and illus- 

 trated and comparative tests, using different grains, are reported. The tests 

 were divided into (1) a comparative accomplishment test of the unused mills, 

 (2) a duration test, and (3) a second accomplishment test of the used mills 

 after being subjected to the first two tests. 



The amounts of coarse meal ground exceeded the amounts generally claimed 

 for the machine by the manufacturers, but the amounts of fine meal were gen- 

 erally less than claimed. The power utilization was greater than claimed, 

 and when the mills were running empty varied between 0.22 and 0.53 horse- 

 power. 



Only three of the mills were able to grind oats to a fine meal. Generally a 

 better degree of fineness of the ground product was obtained with the stone 

 mills than with the other two types. Any desired degree of fineness of meal 

 ^vas, however, more readily and cheaply obtained with the roller mill, and the 

 toothed disk and roller mills were the more suitable for the production of coarse 

 and medium meal. 



The hourly capacity of the roller and toothed disk mills exceeded that of the 

 stone mills, while the stone mills were more easily cleaned and less noisy. 



A magnet was satisfactorily used in six of the mills for excluding foreign 

 metal bodies, but the success of this method is found to depend not only on the 

 strength of the magnet but on its ai-rangement, location, and inclination. 



Handling silage, L. W. Chase and I. D. Wood {NeJjraska Sta. Bui. 145 

 {1914), PP- 5-25, figs. 19). — This bulletin gives general information regarding 

 cutting and loading corn for silage, silage cutters and cutting, filling and seal- 

 ing silos, and removing silage from pit and above-ground silos by means of 

 hand, horse, and mechanical power, and general cost data on silo filling. 



For cutting corn the use of com knives is considered advisable only on very 

 small jobs and then only when sled harvesters or corn binders are not avail- 

 able. The sled harvester is said to be probably the cheapest of the three 

 methods, but the corn binder is considered to be the most satisfactory. 



