APPENDIX.

Judging from the comprehensive title of this work, andof this Appendix , an idea may be entertained by many ofour readers that it is our intention to go exhaustively intothe improvements which have taken place in the world ofMarine Engineering since the publication of the last editionof this work, which bears date 1872. And fearing thatsuch an erroneous idea may be entertained, we hasten toexplain that the intention of this paper is merely to givean outline of some of the more important changes whichhave taken place since then; and to cite a few of the mostsatisfactory examples of increased speed, reduced expense,improved design, or other general advantage ; for were weto notice the work of every engineer who has introducedimprovements into the marine engine or its connectionsduring these eight years, the space at our disposal wouldhave to be doubled or trebled.

During these years the compound engine has gone onincreasing in popularity, and most deservedly so, until itis now the great, standard engine of modern times, and iswithout a rival to contest its supremacy. In its infancyit encountered difficulties and oppositions of great magni-tude ; but then engineering was more infantile, andengineers more timid. When, in looking back over bygoneyears, one thinks of the names of many great engineers,holding the highest positions in the profession, who strenu-ously opposed its introduction, it is remarkable, as a fact,how signally the principle of compounding weathered thestorm and how great and sterling must have been itsadvantages to hold its own, and to conquer the prejudicesof this same opposition. Of course it is an axiom thatthat which is correct in science must eventually conqueropposition and take its proper place ; but no better argu-ment, if argument were needed to prove the pre-eminentadvantages of the compound principle, exists, than that ithas overcome great opposition in so short a time, and thatit is now unrivalled. And unrivalled it will remain, untila rotary engine, constructed on sound principles andeconomical, comes into the field of engineering, whichmost assuredly it will, be it sooner or later. In 1872 thecompound engine held the premier position amongstmarine machinery, and as it holds the same to-day, wecan point to no changes in principle during these years;but in variation of type and dimensions there have beenmany changes, and in this bustling age, when one enginebuilder outvies his neighbour and disdains to hold asecondary rank in reputation, we are still likely to have

yet many changes of type and many additions to thepresent dimensions of our engines. It is to the advantageof the world, of science, of capital, that this honest rivalryexists amongst our engine makers and our shipbuilders,and commerce may look on complacently and reap thebenefits accruing from their labour. The cylinders of themost popular of all types of engines—that is, the two-cylinder compound inverted direct-acting engine — havegone on increasing in size until a maximum has beenreached, and it has been found necessary to introduce athird cylinder when greater power was desired. The con-siderations which fix the size of a cylinder are practical, forit is found that great difficulties are to be met with inthe construction of cylinders of 100 inches in diameter orupwards ; they are very heavy and unwieldy to be carriedfrom place to place during the course of their manufactureand machining, the steam portfaces are very liable to crack,and even when the engine is finally erected and on boardits vessel, the great weight of all the parts of the enginedepending upon, or contiguous to, this cylinder must alwaysbe a strong practical objection to the adoption of cylindersof such a size. The practice of building horizontal engineshad been considerably more in use up to the year 1872than since, and almost the last pair of large and importantengines built about that time were a mixture of horizontaland vertical. They were fitted on board the S.S. “Montana ”for the Guion line, and were built by Messrs. Palmer andCo., of the Jarrow Works, Newcastle-upon-Tyne , thisfirm at the same time putting a similar pair of engines onboard the S.S. “Dakota" for the same line. The high-pressure cylinder of these engines was vertical, inverted,and direct acting, whilst the two low-pressure cylinderswere horizontal, working on to their cranks by means ofreturn connecting rods, each piston having four piston rods.The low-pressure cylinders were each 109 inches in diameter,with a stroke of three feet. Steam was admitted tothe cylinders by means of a Corliss valve gear somewhat likethat used with Mr. John Spencer’s engines. It was the“Montana ” which had the notorious tubular boiler ofMr. Jordan fitted on board when she first appeared ; butas this boiler was found to be an utter failure, it wasremoved, after a few days’ trial, having caused an enormousoutlay in the experiment, and boilers of the ordinarycircular multitubular type were adopted.

This type of engine, being so extremely complicated inits parts, and so difficult to get at, was never popular,

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