his case; and the error, if any, would add to the apparent amount of
leakage, and so be on the right side. Of course, the record of each
consumer's meter would be taken by the inspector at the end of every
quarter, in order to make out the bill; and the totals thus obtained
would be checked by the gross results indicated by the main dial. In
this way, by a comparison of these results, a coefficient would soon be
arrived at, by which the daily recorded results could be corrected to an
extremely accurate measurement. At the end of the working day, the
engineer has merely to take down from the dial in his office the total
record of air measured to the consumers, also the output of air from the
compressors, which he ascertains by means of a continuous counter on the
engines, and the difference between the two will represent the loss. If
the loss is trifling, he will pass it over; if serious, he will send out
his inspectors to trace it. Thus there could be no long continued
leakage, misuse, or robbery of the air, without the company becoming
aware of the fact, and so being enabled to take measures to stop or
prevent it. The foregoing are absolutely essential adjuncts to any
scheme of public motive power supply by compressed air, without which we
should be working in the dark, and could never be sure whether the
company were losing or making money. With them, we know where we are and
what we are doing.

Referring to the estimates given in Table I., I may explain that the
item of repairs and renewals covers 10 per cent. on boilers and gas
producers, 5 per cent. on engines, 5 per cent. on buildings, and 5 per
cent. on mains. Considering that the estimates include ample fitting
shops, with the best and most suitable tools, and that the wages list
includes a staff of men whose chief work would be to attend to repairs,
etc., I think the above allowances ample. Each item also includes 5 per
cent. for contingencies.

I have commenced by giving all the preceding detail, in order to show
the groundwork on which I base the estimate of the cost of compressed
air power to consumers, in terms of indicated horse power per annum, as
given in Table II. I may say that, in estimating the engine power and
coal consumption, I have not, as in the original report, made purely
theoretical calculations, but have taken diagrams from engines in actual
use (although of somewhat smaller size than those intended to be
employed), and have worked out the