For the purpose of obtaining smaller deviation, one part of the compound acts in opposition to the other, the resolving power of the opposing portion must be deducted in calculating the power of the whole.
Deductions as above under clause C, except that one-third be deducted off ironwork of masts and spars, repairs to and renewal of all machinery (inclusive of boilers and their mountings), and all hawsers, ropes, sheets and rigging.
One-third to be deducted off all repairs and renewals, except ironwork of hull and cementing and chain cables, from which one-sixth to be deducted.
One-sixth to be deducted off wire rigging, wire ropes and wire hawsers, chain cables and chains, donkey engines, steam winches and connexions, steam cranes and connexions; other repairs in full.
In estimating the evaporation to be deducted from the rainfall for the purpose of determining the flow into a reservoir, it is important to bear in mind that the loss from a constant water surface is nearly one and a half times as great as from the intermittently saturated land surface.
From this is deducted the average annual cost of repairs, insurance and renewals, the balance constituting the rateable value.
With further experience it has become obvious that very few reservoirs are capable of equalizing the full flow of the three consecutive driest years, and each engineer, in estimating the yield of such reservoirs, has deducted from the quantity ascertained on the assumption that they do so, a certain quantity representing, according to his judgment, the overflow which in one or more of such years might be lost from the reservoir.
Deductions as above under clause B, except that one-sixth be deducted off ironwork of masts and spars, and machinery (inclusive of boilers and their mountings) .
The process by which the first of these contributions was turned into coin is still obscure; it is clear that the corn when threshed was taken over by certain public officials who deducted the amount due to the state.
The amount is not large, though unfortunately it is not exactly known, owing to the fees being treated in many cases as extra receipts, and deducted from the expenditure of the departments by which they are received, so that this part of the national expenditure is not shown in the accounts at all.