[214] This is her nominal power, but as her cylinder is 87 inches diameter, and stroke 48, the power indicated is from 2700 to 3000 horses.
[215] The compound engine has two cylinders, one frequently double the diameter of the other. Steam at a high pressure is admitted from the boiler into the smaller cylinder, and, after it has driven the piston up or down, it is allowed to pass into the larger cylinder when, by its expansive property, it assists in driving the larger piston down or up. When it has exerted its full expansive effect, it is then in a condition to be condensed; and thus a compound engine combines the advantages of both a high pressure and low pressure or condensing engines. Compound engines are sometimes called “high and low pressure” engines, and there are a great many modifications of them, their principle however, being always the same.
[216] In the course of this work I have frequently had occasion to refer to the skill and genius displayed by the Americans in their adaptation of appliances to reduce or dispense with manual labour, but perhaps none of their inventions with this object in view can be compared with the windlass of Messrs. Harfield and Company (formerly Brown, Harfield, and Company), of London, who, beyond other inventions, have produced in their patent windlass, of which the following is an illustration—
a machine of strength, simplicity, and power, applicable to vessels of all descriptions, which has never been surpassed. This very compact instrument can be worked either by manual labour or by steam, and of its value in the latter case Mr. Harfield remarks: “The two principal points of advantage are (1) that the cable is led from the hawsepipe to the underside of the chain-wheel, then over and half round the side standard (formed like a riding-bit) away to the after stopper, thus forming the strongest means for riding securely; (2ndly), the chain-wheels are not attached rigidly to the windlass, but have a very simple frictional connection which can be set up to any desired extent so as to yield to a heavier strain.”
[217] See [Appendix No. 10, pp. 606-608].
[218] Comparative Statement of Consumption of Coal in various Cunard Steamers.
| Names of Ships. | Indicated Horse-power. | Consumption of Coal per Day. | Consumption of Coal per Indicated Horse-power per Hour. | Consumption of Coal per Mile. |
|---|---|---|---|---|
| Tons | lbs. | Cwts. | ||
| Asia | 1,805 | 78 | 4·0 | 5·6 |
| Arabia | 3,005 | 116 | 3·6 | 7·5 |
| Persia | 4,026 | 150 | 3·47 | 9·0 |
| Scotia | 4,500 | 159 | 3·6 | 9·5 |
| Russia | 2,700 | 95 | 3·28 | 6·0 |
| Parthia | 1,950 | 42 | 2·0 | 3·3 |
| Bothnia | 2,543 | 64 | 2·34 | 4·1 |
| Abyssinia | 2,450 | 91 | 3·46 | 5·68 |
| Marathon | 1,450 | 35 | 2·25 | 2·5 |
| Sidon | 760 | 16 | 1·96 | 1·4 |
| Trinidad | 702 | 16 | 2·11 | 1·37 |
| Nantes | 687 | 15 | 2·03 | 1·38 |
| Sidon | 824 | 19 | 2·15 | 1·14 |
| Nantes | 620 | 13 | 1·95 | 1·32 |
[219] See [Appendix No. 11, p. 608]. For this most valuable and instructive table I am altogether indebted to Mr. Burns, who considers toil a pleasure if he can only furnish information which may prove useful to the public. Indeed, had it not been for him and other gentlemen largely engaged in maritime commerce, who have so readily rendered me their aid (for which I tender my warmest thanks), I should not have ventured to offer to the public so large an amount of purely original matter as this volume contains.