1853] 



ance of tlis e'.igines, except in the case of the South America, (a 

 Hu.lsou ri\-er boat,) in wliieh the}' show the maximum peifoi'm- 

 ance. The data for the calculations were obtained for the most 

 ])art from Stuart's " Na\al and Mail Steamers of the United 

 States." The mean effective pressure of the steam, for the whole 

 stroke, lui^, in oaeh instance been diminished 2 fts. to allow for 

 the reaction of the impei'fectly condensed steam on the other side 

 of the ])iston. The reductions from the fourth to the fifth column 

 were etiected, except in the case of the Humboldt, by multiply- 

 ing by tV (nearly in accordance with the results of certain ex- 

 periments and investigations made by Charles B. Stuart, Esq., 

 Chief Engineer of the U. S. Navy. (See work just quoted, p. 

 183 and fsG.) 



The following results were obtained by diminishing the aver- 

 age boiler pressure 2 lbs., which is about the usual excess of the 

 boiler over the cylinder pressure. 



ERICSSOFS ENGINE. 



27? 



In the two cases of the Arctic and Mississippi, the mean effec- 

 tive cylinder pies-^ure was o'ltained by an indicator. The result^, 

 given foi' the other steam sliips would doubtless be nearer the 

 exact truth if an additional allowance of from 1 to 2 lbs. were 

 made for the greater reaction of the partially condensed steam in 

 the cylindei- than in the condenser. If an allowance of 2 lbs. be 

 made on this aceoi.nt, we obtain the following result. 



Table III. 



nearly to the supposition made in Table III), we find the advan- 

 tage in fitvor of the Ericsson, in so far as it has hitherto shown 

 its capabilities, to bo in the pi'oportion of S to 7'3, or 5 to 6 ; that 

 is, to be in all ])robabiHty, in a ratio lying between these two 

 limits. If we make a com}: arison with the Washington and the 



Humboldt, the highest admissible ratio is found to be — ^nd the 



We conclude therefore that the saving of fuel hitherto effected 

 in comparison with the condensing steam engine, in its most eco- 

 nomical operation, is not more than ^,* and may be as low as |. 



At the same time it is to be observed that if the snppossd in- 

 herent capabilities of the new engine should be realized, the 

 saving effected might amount to no less than 70 per cent. 



2. Weight of the Engine — • Calculation of the Weight of the 

 Engines of the ^nc.s.soH.— Weight of hull, from 1200 to 1300 

 tons, as deduced from the weight of the hull of the Arctic; dis- 

 placement, at 17 feet draft, 2200 tons, as calculated by the 

 builders of the ship; ballast, 200 tons of pig iron; weight of 

 masts and rigging, coal, &c., 100 tons, at the outside : hence 

 weight of the engines and paddle wheels,=2200— 1300— 200 

 — 100=600 tons, or 2200 — 1200—200—100=700 tons. 



I find that the same rule for the calculation of the displace- 

 ment, from the length, breadth, and depth, wdiich gives the dis- 

 placement of the Arctic correctlj'-, and a near approximation to 

 that of American steamships generally, makes that of the Erics- 

 son at 17 feet draft, about 2600 tons, which is 400 tons above 

 the estimate maile by the builders of the ship ; a fact which is to 

 be attributed, doubtless, to the peculiar model of the ship. 



COMPARISON WITH WEIGHT OP STEAM ENGINE. 



The average consumption of anthracite coal by the several 

 steam ships named in the table, is 3-11 lbs. per horse-power per 

 hour. Dividing by r87 and 2-26, we obtain the quotient, 1-66 

 and 1'38. From which it would appear that the advantage is in 

 fa\'or of the caloric engine, in the proportion of 8 to 8-3, for the 

 one estimate of the horse-power developed on the trial trip, and 

 of 5 to 6-9 for the other estimate. If Ericsson's estimate of the 

 power of the engines of the caloric ship should hereafter be real- 

 ized, then the gain in the expenditure of fuel, would be in the 

 ratio of 1 to 3'39. But we shall soon see, in another connection, 

 that the comparison ought rather to be made with the numbers 

 given in Table II. If this be done, (omitting the results ob- 

 tained for the Mississippi and the Arctic, which correspond more 



The numbers given in the s?cond column include the weight 

 of the boilers, water in boilers, coal bunkers, and all appurtenan- 

 ces, together with the weight of the paddle-wheels. 



It appears from this comparison that, in proportion to the actual 

 horse-power, the weight of the Ericsson's engines is about three 

 times as great as the ordinary weight of the engines of sea 

 steamers; and in proportion to the estimated power, more than 

 30 per cent, greater. 



3. Space occupied hy the Engines. — This point has been at- 

 tentively considered by a correspondent of the Journal of the 

 Franklin Institute (see the second February number of the Jour- 

 nal, p. 128), who shows that here also the advantage is on the 



• If ilie comparison be made wIlli ihe Ohio and Georgia, the saving may 

 be nearly 5. 



f This shows the horse-power of the Mississippi developed in ils average 

 performanie. There can he no donbl thai ils (ull power is over 600 ; and 

 llieiefore Ihal Ihe raiio o( the weishl lo ihe hor.<e-power is as low as S2. 

 Besides, ihe weight of " wheels, tools, dnplicale pieces of encine, sinres of 

 the engine deparim<"nl,&i'.,"is set down al 2bS Ions, which isinorelhan 100 

 tonsabov.: what would be deemed a sulficient allowance. Kedufing Ihe 

 loial weight to 400 Ions, we have ihe ratio of 0'67. 



% If we lake ihe lowesi delerminnlion of the horse-power oflhe Ericsson, 

 viz: 243, the ratio oflhe weight to the horse-power comes out 2-S2. 



