June 6, 1878] 



NATURE 



139 



of investigation likewise, and has shown how advan- 

 tageous his experiments with models have been. The 

 present Controller and Constructors of the Navy deserve 

 great praise for giving their steady support and apprecia- 

 tion to Mr. Froude in his experimental work. 



The remaining chapters of Mr. White's book are on 

 Propulsion by Sails and by Steam, and on the Steering 

 of Ships. While well and clearly written throughout, 

 and embodying all the settled science of these questions, 

 these chapters appear to us to be less firmly based in 

 some respects, and to present more controversial matter 

 than the earlier parts of the work. We are unable, for 

 example, to approve of the strong preference expressed 

 for the compound engine over other types of marine 

 engine. Basing his views upon the actual performances 

 of three separate types of engine — the ordinary old type 

 of jet-condenser engine, the surface-condenser type, and 

 the compound type — the author goes on to claim for the 

 last-named enormous advantages. In making his com- 

 parisons and drawing his inferences, however, he seems 

 to us to generalise too freely, and to leave out of con- 

 sideration many facts and circumstances which we are 

 bound to consider before pronouncing in favour of the 

 compound engine. Nor are we by any means alone in 

 calling in question the pre-eminent merits of this form of 

 engine when regarded in the light of general principles. 

 Among others who have expressed similar views we may 

 advert to Mr. Neil McDougall, himself an officer of the 

 Admiralty (Steam Branch), who in 1875 published an 

 essay on " The Relative Merits of Simple and Compound 

 Engines as applied to Ships of War," and who arrived, 

 after a long and patient investigation of the Admiralty 

 and other records, at these conclusions, viz., " That there 

 is no insuperable difficulty in the way of working simple 

 engines at the same pressure as that in use at present 

 with the compound engine at sea. Equal economy 

 might, then, fairly be expected with the simple engine, 

 specially fitted, as with the compound, under ordinary 

 working conditions ; " and, " all available evidence goes 

 to show that it is impossible that the compound engine 

 can be to any serious extent superior to the rival engine, 

 at present pressures, in point of economy." It is worthy 

 of note that the first prize, in a professional competition, 

 was awarded to this essay, the judges being Prof. Cot- 

 terill, M.A., F.R.S. ; Chief Inspector W. Eames, R.N., 

 the Chief Engineer of H. M. Dockyard, Chatham ; and 

 the eminent engineer, J, Penn, F.R.S. 



The rapid perusal which alone we have been able to 

 give to this large volume of more than 600 pages has 

 disclosed to us but few blemishes, and these, for the 

 most part, of the slighter sort, and such as are chiefly 

 due to brevity of treatment. We will refer to those only 

 which we observe in the first chapter. The remark that 

 the equality existing between the total weight of water 

 displaced by a ship and her own weight " is equally true 

 of wholly submerged vessels as of ships of ordinary form 

 having only a portion of their volume immersed," will 

 create difficulty in the minds of some of the readers for 

 whom the work is intended. The principle is doubtless 

 true of vessels which just float, without any reserve of 

 buoyancy above the water's surface, and which, therefore, 

 are wholly submerged ; but its obvious inaccuracy when 

 applied to the Vanguard^ the Eurydice, the Grosser 



Ktirfiirst and other ships which are very unfortunately, 

 but nevertheless very certainly, "wholly submerged" 

 points to the necessity for a modification of the language 

 employed. Again, the statement that " the weight of the 

 ship in tons multiplied by thirty-five gives the number of 

 cubic feet in the volume of displacement " may puzzle 

 some young readers of the work— and there should be 

 many young readers of it among the naval cadets and 

 others —who may fail to see that the number " thirty- 

 five" is derived from the previous statement that 64 lbs. 

 is the weight of a cubic foot of sea-water. It is impos- 

 sible to make these elementary matters too clear for 

 young sailor-officers. Such students will also require 

 some assistance in understanding the paragraph in which 

 the author explains the pressures acting on the bottom of a 

 ship. Following the mathematical method of assuming 

 the existence and action at every point of a pressure acting 

 " perpendicularly to the bottom," and treating this as 

 made up of three components, the author justly speaks 

 of the vertical components only as affecting buoyancy, 

 and no less justly dismisses the horizontal components, 

 as they must, on each set, " obviously be exactly balanced 

 amongst themselves." No youngster accustomed to the 

 mathematical treatment of forces or pressures will find 

 the slightest difficulty in all this ; but we can well imagine 

 less favoured sailors, of all ages, pausing at the statement 

 that the water pressure can "at every point" be resolved 

 into three such components, and searching in vain for 

 horizontal pressures, for example, under the flat bottom 

 of a ship. It is, we are well aware, impossible to avoid 

 difficulties of this kind without great elaboration ; but we 

 hold it to be a primary necessity to avoid them to the 

 utmost possible extent in a work like this, which 

 has been expressly written for those very many per- 

 sons, outside the naval architect's profession, who 

 are " more or less intimately connected with ship- 

 ping," and desire to get some knowledge of the sub- 

 ject. In one important respect Ave think the author's 

 explanations of the sub-division of ships into compart- 

 ments, and of the consequences of admitting water into 

 them, much too brief, viz., that of the division of ships 

 by middle-line bulkheads. This is dismissed with the 

 remark that the advantages of such bulkheads are too 

 obvious to need comment; but however obvious the 

 advantages of the system may be, the efifects of admitting 

 water to the divisions so obtained should certainly have 

 been investigated and set forth. In any case it would 

 have constituted both an interesting and an instructive 

 branch of the subject other parts of ^which the author 

 has treated so fully and so well ; but the recent improve- 

 ments in the Alexandra and other twin-screw ships has 

 made it also a subject of great importance. The intro- 

 duction of the middle-line water-tight bulkhead wherever 

 it could be applied is one of the most valuable of the 

 many valuable improvements introduced by Mr. Barnaby 

 and his stafT since the first charge of our Admiralty Naval 

 Construction became theirs, and officers who are " ship- 

 mates" of this system (to use a naval phrase) will be 

 disappointed to find it so summarily dismissed from the 

 author' s and the reader' s notice. The defect is the more 

 obvious because of the singular clearness and fulness 

 with which the general question of sub-division is ex- 

 pounded. The task of mentioning the blemishes and 



