14 BULLETIlSr 423, U. S. DEPARTMENT OF AGEICULTUEE. 



DEPRECIATION. 



It is not possible, in view of the short time the mechanical milker 

 has been in general use, to secure accurate data on the rate of de- 

 preciation of such machines. Some of the parts, such as the vacuum 

 tank and the iron piping, should last almost indefinitely. The 

 jDails, if heavily nickeled or made of nickel alloy or other noncor- 

 rosive metal, should last for a number of years. The parts most 

 subject to depreciation, the rubber tubes and teat cup rubbers, are 

 normally subject to such frecpient renewal that the cost of keeping 

 them u]D has been included under repair costs. The parts always 

 subject to a certain amount of wear are the engine, pump, and pul- 

 sator. Reliable data is at hand to justify the assumption that the 

 depreciation of the small stationary engine averages not more than 

 10 per cent per year. Since the pump is much less complicated 

 than the engine and is not subject, as is the engine, to deterioration 

 due to excessive heat, it may be assumed that the life of the pump 

 -is somewhat longer than that of the engine. This leavgs the pul- 

 sator, the cost of which is not more than 25 per cent of the total cost 

 of installation, as the only wholly unknown quantity. All things 

 considered, it has been thought safe to assume that the life of the 

 outfit as a whole, not counting rubber parts, is slightlj^ longer than 

 the known life of the engine. Hence 8 per cent per year has been 

 taken as the rate of depreciation of milking-machine outfits in this 

 discussion. It should be borne in mind, however, that this figure 

 is a somewhat arbitrary one, used in this connection only for lack 

 of any more definite figure and that it applies to the entire outfit, 

 exclusive of rubber parts. It was felt that the use of even this rough 

 approximation would tend to make the results of this study more 

 reliable than they would have been had depreciation been ignored 

 altogether. 



The depreciation charge, like the investment charge, is affected 

 by the initial cost of the milking outfit. 'Wlien an arbitrary depre- 

 ciation figure is applied to all outfits the more expensive ones re- 

 ceive a higher depreciation charge. In actual use, however, the de- 

 preciation is determined by the initial cost and the length of life 

 of the machine, with the last factor the more important. 



COMPARATIVE COST OF MILKING BY HAND AND BY MACHINE. 



As previously stated, the cost of l>and milking is determined by the 

 time taken to milk and the wages paid to the milkers. In figuring 

 the cost of milking with the mechanical milker the following items 

 Avere considered in addition to the labor cost: The interest on the 

 investment, the fuel expense or cost of power, and the repairs and 



