332 Wear and Tear of Agricultural Steam- Engines. 
expense in repairs or renewal of the parts, such as the drum or 
concave, ought not to occur for many years after erection ; and 
the usual wearing of brasses, and straps, and other small items of 
expense, ought not to exceed 3Z. a year for a term of 14 years. 
We make the following extract from a letter of Mr. John 
Sowerby, jun., of Beelsbey, who has two barn-works — erected in 
January, 1856, and November, 1857 — which thresh the growth 
of 400 acres of corn a-year : — " The barn-works have cost for 
repairs, about 3Z. 9s. Qd. for one of them until July, 1857, and 
for l)oth l)arn-works from that time until December 31, 18(31, 
about 9Z. Gs. bd., besides 14s. GrZ. for a set of knives for the barley- 
awner. They were not looked over last summer, but are in good 
working order." This is only IZ. 3s. *dd. per annum for each, for 
four years. 
Tliere is, however, a liability in this, as in the portable machine, 
to outlay in introducing modern improvements into the working- 
parts ; with this in view the machine should be made as simple 
as possible, and the dressing apparatus should be sepai-ate. 
7\s a basis for calculations in our attempt to estimate the 
exact amount of depreciation, we will suj)pose the fixed machine 
to be worth lOZ. to 30Z. at fourteen years old ; it will probably 
be worth more, but the valuation ought, on principle, to be low, 
for it Avill be remembered that our charge of 3Z. a year for 
repairs has not provided for effecting any heavy item of renewal 
•or improvement. 
TahJi; showing amount: of llepuirs and Depreciation for Portable ThresJiint/- 
Mach ines — Singte-Blast. 
Ilorse-power. 
]'rice. 
Supniisetl 
Value in 
10 Years. 
Amount of Depreciation 
and Interest per Annum lor 
10 Vears. 
Amotint of 
Ilepairs per 
Annum for 
10 Years. 
£. 
£. 
£. s. £. s. £. s. 
£. s. 
•1 
85 
10 
9 14 + 0 10 = 10 4 
8 1) 
7 
100 
10 
11 12 + 0 10 = 12 2 
9 0 
Repairs, ^( 
;;for Portable Threshing- Machines — Double and Treble Blast. 
5 
95 
10 
13 0 4- 0 10 = 13 10 
10 0 
7 
110 
15 
14 12 + 0 15 = 15 7 
12 0 
8 
120 
20 
15 4 + 1 0 = 16 4 
14 () 
