890 EXPERIMENT STATION EECOED. [Vol.36 



A standard drawbar rating for tractors, R. Olney {Farm Machmcry, No. 

 1291 (1916), pp. lS-15, figs. 2; Power Farming, 25 (1916), No. 8, pp. 9, 50-52, 

 fig. 1). — In an address before the National Gas Engine Association, the author 

 advocates the rating of tractors on the basis of the actual pounds of pull 

 developed at the drawbar instead of on the horsepower basis and reports 

 experimental data to substantiate his argument. Motor torque and brake 

 horsepower curves, reproduced from the data obtained from an actual prony 

 brake test on a 3^ by 5^ tractor motor of the 4-cylinder, heavy-duty type. 

 are given showing that the torque and likewise the pounds of drawbar pull 

 remain practically constant throughout a wide range of motor speeds, while 

 the brake horsepower varies directly as the speed up to a certain point. 



"A prony brake test should be made on the motor to obtain data for deter- 

 mining the torque and brake horsepower at various speeds. The torque curve 

 of any motor . . . will indicate the normal or critical speed of the motor or 

 the speed at which the motor produces the greatest torque. The brake horse- 

 power rating should be given on the basis of the torque produced at this speed. 

 The basis for the drawbar rating should be the pounds pull exerted in an 

 actual pulling test. The drawbar test should be made with the motor running 

 at its critical speed and with the tractor traveling at its best working speed 

 as fixed by the gear ratio." 



Controlled tests of mechanical cultivating apparatus, Ringslmann et al. 

 (Compt. Rend. Acad. Agr. France, 2 (1916), No. 22, pp. 609-615). — This is a re- 

 view and summary of the results of several different trials. 



Tobacco-curing bams, E. G. Moss (A'^. C. Agr. Ext. Serv. Circ. 18 (1916), pp. 

 9, figs. 5). — This circular, prepared under a cooperative agreement between the 

 North Carolina Experiment Station and the U. S. Department of Agriculture, 

 reports an experiment in tobacco curing begun in 1911, the object being to 

 determine where more uniform curing, considering weather conditions and 

 varying amoimts of water in the tobacco at the time of curing, can be made 

 and " whether the fuel consumption could not be materially reduced by using 

 tight barns fitted ■oath proper ventilators so placed in the barn as to keep a 

 current of air circulating through the tobacco when needed. 



" For this experiment two 18-ft. log barns were \ised. On one of these the 

 old roof was replaced by a tight cover of galvanized V-crimp iron. Between 

 the sheeting 1-in. strips were nailed to prevent air escaping around the eaves 

 of the roof. The brrn was daubed inside and out so as to make it as nearly 

 air-tight as was practical. Seven 4-in. pieces of terra cotta pipe 2 ft. long 

 were placed in the underpinning of the barn, the bell of the pipe being flush 

 with the outside of the barn and extending inside the barn and delivering the 

 air either under or against the sheet-iron pipes used as flues. By this means 

 the air is slightly heated before coming in contact with the tobacco, and con- 

 sequently more quickly absorbs the moisture from the green tobacca A type 

 of inverted trough ventilator . . . was placed on top of the barn. . . . The 

 second barn . . . was covered with boards, was well daubed outside, and fitte<l 

 with the same size furnaces and flues as the tight barn. Each of these barns 

 would hold about 400 sticks of cut tobacco." 



It was found that a saving of 2i cords of wood was effected in the tight barn 

 during four curings, which Is considered to be a considerable advantage. Plans 

 and a bill of material for a barn of this type are included. 



Lightning rods; their functions and good qualities, T. Cboft (Farm Ma- 

 chinery, No. 1293 (1916), pp. 35-37, figs. 8).— This article deals with the devel- 

 opment and effectiveness of lightning rods and with their instnllatioa and pro- 

 tection. 



