730 EEPOET— 1889. 



industry, and of collecting aU the available literature on the subject. It is need- 

 less to remark that Dr. Mendeleeil's views are not shared by every competent 

 authority ; nevertheless the remarkable permanence of oil-wells, the apparently 

 inexhaustible evolution of hydrocarbon gases in certain regions, almost forces one 

 to believe that the hydrocarbon products must be forming as fast as they are con- 

 sumed, that there is little danger of the demand ever exceeding the supply, and 

 that there is every prospect of oil being found in almost every portion of the 

 surface of the earth, especially in the vicinity of great geological disturbances. 

 Improved methods of boring wells will enable greater depths to be reached ; and it 

 should be remembered that, apart from the cost of sinking a deep well, there 

 is no extra expense in workuig at great depths, because the oil generally rises to 

 the surface or near it. The extraordinary pressures, amounting to 300 lbs. per 

 square inch, which have been measured in some wells seem to me to yield conclu- 

 sive evidence of the impermeability of the strata from under which the oil has been 

 forced up, and tend to confirm the view that it must have been formed in region* 

 far below any which could have contained organic remains. 



The weights and measures in use in this country are a source of considerable 

 trouble and confusion. Besides the imperial measures, which are complicated 

 enough, a great number of local units are in use, so that unwary strangers are not 

 unfrequently deceived, or, at any rate, if they hope to escape from mistakes, have 

 to apply themselves to the study of local customs. In the scientific world, again, 

 the metric system is now almost exclusively used, and the same may be said of 

 engineers and manufacturers who have to do with foreign countries in which 

 French measures are in vogue. The same ditficulty surrounds the measurement 

 of the power of motors. The unit of power is, indeed, from the nature of the 

 case, common to the whole world — it is unit of weight multiplied by unit of height, 

 — and with us the foot-pound, or 33,000 times the foot-pound, is generally accepted ; 

 but the difficulty lies in determining how the measure is to be applied. Thus, in 

 the case of a water-motor — should the power be calculated by the energy latent in 

 the falling water, or in the actual work given off by the motor ? In heat engines 

 we have to deal with many variables. There is the initial pressure of the working- 

 agent, the terminal pressure, the length of stroke, the number of revolutions 

 per minute, the indicated power in the cyHnder, the effective power given off, and 

 the adequacy of the means of supplying the working agent. In the early days of 

 steam, when pressures were pretty uniform, and speed bore a certain relation to 

 the stroke, the diameter of a cylinder was a tolerably close index to the power of 

 the engine, and such simple rules as ' 10 circular inches to the horse-power,' which 

 prevailed among agricultural engineers, were tolerably intelligible. But in these 

 days, when pressures, speeds, and rates of expansion vary so greatly, the size of the 

 cylinder, or cylinders, is no longer a guide, and I imagine that, most manufacturers 

 have ceased to class their engines by their nominal horse-power. The problem is 

 pretty simple in the case of pumping engines, for there the nominal power may be 

 taken, as it is in Holland, to be the actual work performed upon the water, and 

 perhaps a similar rule might apply to motors driving dynamos, but for most other 

 purposes no simple law is possible. In my own practice I have, for many years, 

 been in the habit of classing engines by the indicated horse-power per one revolu- 

 tion for every probable initial pressure, below the maximum one for which the 

 engines were designed, and for various rates of expansion. To facilitate the cal- 

 culations I use curves which give ilio theoretical horse-power, on the supposition 

 that steam expands according to Boyle's law, for 10,000 cubic inches of steam 

 measured at the moment of exhaust, which is, in fact, the volume of the cylinder 

 in single-cylinder engines, and the volume of the last cylinder in compounds. 

 These curves are calculated for initial piessures rising by 25 lbs., and, in non- 

 condensing engines, for the extreme range of expansion possible, and to fourteen 

 expansions in condensing engines. The true indicated horse-power ranges from 

 80 per cent, to 85 per cent, of the theoretical, as above stated, the precise per- 

 centage depending upon the construction of the engine. As large engines are now 

 almost always compound, the size of the cylinders is no guide to the lay mind; 

 hence, in answering inquiries, it is necessary by some means to get at the actual 



