ERICSSON'S ENGINE. 



[185S 



side of the steam engine ; — tha economy of space being nearly 

 twice as great. 



4. Frklion and oilier Reahtanccs. — AVe may obtain an es'i- 

 mate of the comparative resistance, in the t«o forms of engine, 

 to be overcome by the mo\ing power, by reducing the power of 

 the steam engines to the speed and immeisi'd mids' ip sec- 

 tion of the Ericsson on the occasion of the trial trip; that is, 

 calculate what reduced power they would have if they wei'e just 

 capable of propelling wilh a speed of 7 o.[ 7i- miles per hour, the 

 ships in which they are placed, if the area of theimmereed mid- 

 ships section were the same as that of the Ericsson at 17 feet 

 draft, i. e. 520 square feet. This may be effected by obser\ing 

 that the horse-power will vary nearly as the cube of the velocity 

 multiplied into the area of the transverse midship section. This 

 is quite near the truth, if we suppose the diminution of power to 

 be accomplished by reducing the area of the piston, and other 

 parts of the engine proportionally ; the pressure of the steam, cut 

 off, and all other circumstances i emaining the same. The follow- 

 ing table contains the results of a few cidculations made by the 

 rule just stated. 



These determinations, although they differ considerably among 

 themselves, as was to be expected, from the vaiiety of size and 

 model of the htills of the several vessels selected, as well as of 

 construction and operation of the different engines, and are not to 

 be regarded as veiy exact, still serve to show that no just claim 

 can be set up of superiority on the part ol the hot air engine 

 over the steam engine, on the ground that the resistance incident 

 to the movement of the engine is decidedly less. Also, on ob- 

 serving that 'he horses-]iower given in Table II. were used in 

 making the calculations for the Washington, Fulton and South 

 America, it will be seen that the statement just made is still tiue 

 if we include among the several resistances in play in the steam 

 engine, the excess of the reaction of the partially condensed 

 steam in the cylinder over that of the same in the condenser. 

 We may hence conclude that we were justified in making the 

 statement that the comparative consumiition of fuel b}' the two 

 engines, in producing the same useful effect, is to be ascertained 

 by taking the deterniin:itions of expenditure given in the last 

 column of Table 11, rather than the hii-gcr values to be found in 

 Table III. 



5. Adaptation to the production of high velocities. — At 

 double the speed of the Ericsson on the trial trip, that is at 14 to 

 15 miles jier hour, the hoise-power wouM be about eight times 

 greater, or about 2400; and the quanf'ty of coal consumed, de- 

 duced from the present capabilities of the engine, would be eight 

 times greater, or 48 tons ])er day. This supposes the draft to 

 remain the same, wheieas it will be materially increased hy the 

 necessary augmentation of the weight of the engines. In fact 

 the weight of the engines at the speed supposed wfiuld be about 

 three times as great as their present weight. At her present 

 draft, (viz^ 17 feet,) an .additional weight of 200 tons would sink 

 the hull of the Ericsson one foot. Taking the lowest estimate of 

 the weight of the present engines, (GOO tons), the neje.ss.ary ad- 

 dition of weight would not be less than 1200 tons; which would 

 sink the hull nearly 6 feet, or increase the draft to about 23 feet, 

 that i.s, make tlie draft .after the 200 tons ballast is removed, 22 

 feet; which is from 1 to 2 feet deeper than the load-line. The 

 midship section would thereby be enlarged to 720 square feet. 



and therefore the power necessary for the proilnction of the 

 double velocity augmented in the proportion of 520 to 720. If 

 this be done, we lind the required liorsb-puwer to be 3;J20. The 

 coi'responding consumption of coal would be 66 tons |>er day. 

 Now, even at 50 tons jier day, the stock of coal required for a 

 transatlantic voyage of 12 days duration, would not be less than 

 GOO tons; which would produce an additional depression of the 

 hull of nearly 3 feet, or sink it some 5 feet deeper than the load- 

 line. If it should be maintained that the weight of the engines 

 would not be more than doubled, the depression pi-oduced by the 

 engines and the necessary supply of coal would stili be below the 

 load-line. Again, if it should fie conjectured that the eonsump- 

 ■tion of coal will not be augmented, in the case of the caloric 

 engine, in the .-ame proportion as the real horse-power, to show 

 th.it this supposition is erroneous it is only necessary to stale that, 

 as a mattei' of fact, the amount of coal consumed for each horse • 

 power by the engines of the Ericsson, is even greater than that 

 consumed by the stationary caloric ei'.gine. Ericsson gives 60 

 as the horse-power of the stationary engine, and 0-6 lbs. jier 

 horse-power per hour as its consumption of fuel, and 600 and 

 0'9 lbs. as the corresponding quantities in the case of the Erics- 

 son's engines. 



Let us now see what will be the result in case the estimated 

 capabilities of the caloric engine should be realized. If the 

 horse-power should be increased from 300 to 600. the speed of 

 the ship would be increased nearly in the proportion of the 

 ^300 to the ^000, or of 6-69 to 8-43 ; that is, to 8-82 or 9-45 

 miles per hour, according as the speed on the trial trip is taken 

 at 7 or at 1\ miles. To obtain a speed of 15-5 miles, which is 

 the speed ( f the Arctic in still water, the expenditure of fuel must 

 bo increased in the proportion of (8-8-)3 to (15-5)*, or from 6 to 

 33 tons, disregarding the increase < f draft. As a matter of fact 

 the weight of the engines will be augmented in about a two-fold 

 ])ropoi'tiou, which will increase the di'aft nearly 3 feet; or make 

 the di-aft, after the ballast is remoxed, about 19 feet, an I therebv 

 augment the necessary consun-ption of fuel to 38 tons. The 

 supply of coal for a 12 days voyage, at 50 tons per day, would 

 be 600 tons; this additional load would increase the draft on 

 lea\ing port to 22 feet, which is some 2 feet deeper than the 

 load-line. 



If we take the other estimate of the velocity answering to 600 

 hoi'ses-powei', \'\z., 9-45 miles, the amount of coal requii'cd, at the 

 velocity of 15'5 miles in sti!l water', will be about 30 tons per day, 

 or 450 tons for a voyage of 15 davs. The addition to weight of 

 engines will not be less than 360 tons; and 360-l-450=8l6 tons 

 will just sink the ship to the loaddine. 



The Arctic would accomplish the voyage in the same time, 

 and carry not less than 700 tons freight. But in doing this her 

 engines w. mid consume about 600 tons more coal than those of 

 the Ericsson in the case supposed. This estimate, of the highest 

 possible performance of the Er-icssm, is so near an approximation 

 to the pei'formance of the steamships of the Collins' line, th.at it 

 must be admitted to be within the bounds of possibility that ca- 

 loric shi]is may hei'cafter comjiete successfully with these cele- 

 bi'ated steam-ships. At least this conclusion seems to follow, 

 unless we have underrated the necessary weight of the caloric 

 engines. It must be left to time to decide the question, whether 

 the full estimated power of tire caloric engines can be actually 

 obtained ; and whether', tlier'efore, the results which ha\e been in- 

 dicated, will, fr'om being a mere ideal limit, ever come to bo an 

 actu.al realization. 



With her present capabilities the aver.age speed of the Ericsson 

 at sea would not exceed 6 miles per hour, (see Journal of the 

 Franklin Iirstitute for February, NV 2, p. 127); and she would 

 require 24 days to peiform the voyage to Liver'pool (3550 statute 



