588 EXPERIMENT STATION EECORD. 



from an implement the greater is its total of days and acres of work done 

 before wearing out, and the less is the interest charge per acre and per day 

 actually used, 



" The replacement cost per acre or per bushel or ton is from two to seven 

 or eight times as great for small acreages as for large acreages. The farmer 

 with a small acreage can not compete in economy in the use of machinery with 

 the farmer having a larger business. With the best of shelter and care, the 

 small farm can only hope to equal the replacement cost per unit enjoyed by the 

 large farm; it can not hope to avoid higher interest charges. As a rule, it is 

 not profitable to build for machinery any special shelter which adds over 15 per 

 cent to the total machinery investment on a farm. Repair charges per machine 

 increase with increasing use, but not in proportion to the amount of work done. 

 Repair charges per acre and per day decrease as the acreage covered annually 

 increases. The larger and more substantial sizes of machinery give cheaper 

 service than the lighter sizes, since the cost for repairs is much lower for the 

 heavy machine than for the lighter machine, while the first cost is but a 

 fraction gi-eater." 



Competitive tests of agricultural machinery, .\lbert, Fischer, and Reiser 

 (Arb. Deut. Landic. Gesell, No. 273 (.1915), pp. 15, figs. 92).— This is a classi- 

 fied report of trials of a number of recent developments in agricultural 

 machinery, especially mowing machines, hayrakes, and hay tedders. 



Boiler laws and their relation to traction and portable engines, G. G. Dana 

 and J. Mainland {Amer. Thrcshcrman, 17 {IHI.',), Xos. 6. pp. 2S-32, figs. 2; 

 7, pp. 4'h 45, figs. 2; 8, pp. 30-32, 81). — It is the purpose of this article to point 

 out some of the differences existing in the various laws regarding boilers in 

 some of the States and in the neighboring Canadian Provinces, and to compare 

 their relative merits in the hope of promoting uniformity in boiler laws. 



It is concluded that each one of the laws discussed is good individually and 

 that a boiler constructed in compliance with any one of them would be safe 

 and durable, but that it is difficult for a manufacturer to build a boiler that 

 meets the requirements of them all at the same time. 



The Canadian method of having boilers and appliances approved is recom- 

 mended as having an advantage over the procedure in the United States. 

 "Boiler materials as specifie<l by the Alberta and Saskatchewan rules seem 

 better adapted to the various parts than those specified by the other rules. 



" The results obtained from figuring the efficiencies of joints agree very closely 

 when obtained by the different formulas . . . but the Ohio and Massachusetts 

 methods seem more comprehensive and rational. However, their rules make no 

 mention of the distance between rows of rivets, while all the Canadian rules 

 cover this point in a very elaborate and cumber.some manner. . . . 



" A graduating factor of safety as adopted by the Canadian rules to take care 

 of the different types of joints, class of workmanship, and designs apparently 

 has an advantage over the Ohio and Massachusetts method of restricting the 

 use of lap joints on the longitudinal seams to pressures under ICX) lbs. and 

 using five as a constant factor of safety for all constructions. The drilling of 

 rivet holes from the solid plate or roaming them a liberal amount from a hole 

 that has been punched is no doubt a step toward safety, and the rules regarding 

 this point as given by Ohio and Massachusetts, if revised as suggested, would 

 facilitate manufacturing without weakening the construction." 



"There is a wide difference in regard to the working pressures allowed on 

 flat surfaces by the various rules. Alberta being the most stringent and British 

 Columbia the most liberal. . . . The portion which is considered self-supporting 

 on heads of boilers is nmch less for Alberta than for British Columbia, while the 

 rules for Ohio and Massachusetts make a uniform allowance regardless of the 



