Nov. II, 1880] 



NATURE 



27 



circumstance that in the case of the coke-gas fire no heat 

 flashes up the chimney, but is utilised entirely for raising 

 the coke in front of the grate to the condition most 

 favourable to radiation into the room. 



I hold that it is almost barbarous to use raw coal for 

 any purpose, and that the time will come when all our fuel 

 will be separated into its two constituents before reaching 

 our factories or our domestic hearths. Such a measure 

 would not only furnish us with the complete solution of 

 the smoke question, but would be of great value also as 

 a money saving. In conclusion I may observe that I 

 have taken up this question without the idea of profit, 

 and shall be happy to furnish builders and others desirous 

 to introduce the grate here described with the necessary 

 indications to insure success. C. William Siemens 



THE RUSSIAN IMPERIAL YACHT, "LIVADIA " 



IN Nature, vol. xxii. p. 270, we gave an account of 

 this remarkable ship, and stated that we should 

 report the results of her trials to our readers. We there 

 said " it cannot be doubted that her speed will surpass 

 14 knots," and we pretty plainly intimated that it would, 

 in our judgment, fall substantially short of 17 knots ; in 

 point of fact it has fallen between these limits, and nearer 

 the higher than the lower, the average mean speed at the 

 measured distance being I5"S64 knots. The details of 

 the several runs, which have not previously been published 

 in London, we believe, are as follows : — 



Average 12,354 IS725 



The trials of the Livadia were greatly hurried, the 

 vessel going down the river on a Wednesday, making a 

 preliminary run under steam on the following day, 

 Thursday ; on Friday she made a run at full speed for 

 six hours, giving an average of 15 knots ; and on Saturday 

 she made her measured mile trials. Those who under- 

 stand the conditions under which these steam trials were 

 made will see at once that it was not possible to obtain 

 the best results with a ship thus put under steam day 

 after day, her boiler tubes getting doubtless more or less 

 foul, and her machinery also falling somewhat out of 

 perfect condition, especially where there were three 

 separate sets of engines to be cared for. The bottom was 

 also foul from having been three months in the wet dock 

 at Fairfield. The effect of haste in making the trials is 

 visible in the variations of horse-power developed upon 

 the nins, there being a difference of more than 1000 h.p. 

 between the power developed, for example, on the second 

 run as compared with that of the fifth. The speeds given 

 above show less discrepancies than the horse-powers, but 

 it can hardly be doubted that the Livadia as she is can 

 be driven at over 16 knots under fair conditions, without 

 any alteration whatever. It is, as has been said else- 

 where, highly probable that some improvements might 

 be made in the screw propellers, as it is not to be 

 expected that the best conditions were secured at the 

 first attempt. In fact we have evidence that the central 



screw was set at a pitch different from that of the side- 

 screws, and runs at a diflerent speed; it now appears 

 likely that the pitch should have been the same in all 

 cases, and when the opportunity offers this change will 

 probably be made, and the speed again taken. Other 

 slight modifications will doubtless also be tried, and 

 those of our own naval architects, who have well con- 

 sidered all the facts, have formed the opinion that if all 

 minor causes of interference with the best performance 

 are removed, a speed approaching 17 knots may be 

 reached in the Livadia. It needs no words of ours to 

 convince the scientific world that whether any great 

 increase of speed be obtained with this vessel or not, 

 the Russian Government has rendered a vast service to 

 naval science by demonstrating on a large scale and in a 

 public and unquestionable manner, the fact that a vessel 

 whose breadth is enormous, and whose length is but one 

 and a half times her breadth, may with no very inordinate 

 expenditure of power be made to take a high place 

 among the few fastest ships of the world. 



But the interest in the Livadia, while it is greatest as 

 regards her high-speed trials, by no means ends there. 

 Her steaming performances with diminished steam power 

 are also very interesting. In considering these the reader 

 should remember that in this case as in all cases of fast 

 ships going with reduced power and at reduced speed, 

 the performances are subject to a double disadvantage : 

 first the ivcight of the machinery carried is of course in 

 excess of what is needed to produce the reduced power ; 

 and secondly, the friction and other losses are likewise in 

 corresponding excess. For example, when the Livadia 

 is steaming say at 11 to 12 knots, she is employing less 

 power than any one of her three sets of engines produces ; 

 and if she had not to go beyond such a speed she might 

 dispense with the other two sets of engines and boilers, 

 and thus be relieved of nearly 1000 tons of weight, and of 

 two-thirds of the frictional and other losses which she is 

 obliged to undergo when steaming at 11 or 12 knots Avith 

 all her engines working at a reduced speed. Bearing 

 these facts in mind, we may now state that the reduced 

 steaming of the Livadia is reported officially to have 

 given the following results : — 



Aggreg.ite Soeed 



Ind H.P. ^P"*^- 



2969 ... II knots 



4770 ... 13 .. 



8940 ... 15 ,, 

 10,037 ... I5.i ,, 



The indicated horse-powers above given were calculated 

 from diagrams, and the speed was taken by log. The 

 results were reported, we know, in perfect good faith, and 

 are a correct indication, in the main, of the relation 

 between power and speed in the Livadia with her present 

 screws, &c. They nevertheless appear to us to exhibit 

 on the face of them some slight discrepancy, which is 

 amply accounted for by the fact that the speeds were, as 

 we have said, taken by the log, which does not admit of 

 that minute accuracy which may and ought to charac- 

 terise measured mile-trial results. The above figures are 

 borne out by the sea-passages of the yacht. She steamed 

 continuously in fair and moderate weather at an average 

 speed of somewhat more than 12 knots with an average 

 expenditure of about 4000 Ind. H.P. 



With all the above facts and figures before us we see 



Wind. 



With. 

 Against 



Tide. 

 Slightly 



Slightly against 

 Aijainst 



