333

For the Journal of the F r a n k l i n Ins t i tu te .

-Particulars of the Steamer James ./t. Requa. Hull built by Harlan & HolIingsworth, Wilmington, Delaware.

tended service, New Grenada. In-

~IuLL.- -

L e n g t h on deck , . . ~14 feet. " " be tween pe rpend icu l a r s , 210 "

B r e a d t h o f b e a m , 32 " D e p t h o f hold, 7 "

" " to spa r deck, 7 " L o a d d ra f t , 2 " 6 inches. Tonnage, . . 450. Area of immersed section a t load draf t , 70 "

E~GlXZ~ . - - Inc l i ned d i rec t n o n - c o n d e n s i n g .

D i a m e t e r of cyI inder , 24 inches. Lcl~gth o f s t roke , . . 8 feet. W e i g h t o f engines and wheels, 2 1 0 , 0 0 0 lbs.

B mI, n n s . - - F i v e - - C y l i n d r i c a l - - f l u e d .

L e n g t h o f boi lers , 35 feet . B r e a d t h " 3 " 6 inches. W e i g h t of " witl~out wa te r , 120,000 lbs. L o a d o n sa fe ty -calve, per sq,uare i n c h , 140 lbs. Number of furnaces, . 5. B r e a d t h o f " (?) 18 " 6 " L e n g t h o f grate bars, . 6 " 1Number of f lues, 10. Internal d i a m e t e r of flues, 15 "

L e n g t h of flues, 34 " H e a t i n g su r face , . 2400 sq. it, D i a m e t e r o f c h i m n e y , 5 " I t c i g h t " , 5 0 " 9 ,c

PADDLE WHRELS.-- D i a m e t e r over boards,. 26 feet . L e n g t h of " 8 " D e p t h " 15 i rmhes . .-Number " 19.

Remarks.NFrames, shape L, 3 ins. × 3 ins. × ~ in. and 24 ins. apart. Number of strakes of plates f~om keel to gunwales, 11. Thickness of plates ~t-1~ and ¼ in. :Number of bulkheads, 3. Diameter of rivets, ~ths. Distance apart, 2 ins.; single riveted. Depth of keel, 4 ins. Inde. pendent steam, fire, and bilge pump, 1. Has I t athwartship frames, and 8 side keelsons 12 ins. deep. C . H . H .

For the Journal of the F r a n k l i n Ins t i tu te .

"1reproved Double-Action Force Pump." By ERSI:I~E HAZARD. I was much surprised, on reading the article at page 32, of the Journal

of the Franklin Inslitute, for January last, that none of the Committee on Publications gave our countryman, Jacob Perkins, Esq., the credit of inventing the double-stroke force pump, claimed by Robert Aytoun. It is precisely his single barrel fire and garden engine pump, which ~'as

334 .Mechanics, Physics, and Cl~emistry.

manufactured by him in great numbers in this City, some thirty-five years ago ; and afterwards by his successors, Merrick & Agnew. In those en- gines, an external cylinder, surrounding, and communicating with the top of the pump barrel, by numerous holes, formed the " bent pipe, '~ leading to the air vessel, If I am not mistaken, I have, some years since, seen the same principle applied to common lifting pumps at Car- bondale, a thick pump-rod aetiL~g like a plunger, in keeping up a con- tinuous discharge.

On Working Steam Expa'nsively in .Ma~'ine E~gines. By Mr. E. ALLEN.* (Continued from page 256.)

In the foregoing paper, the object of the author has been merely to collect a few particulars of the dilferent classes of vessels, and to give a rough approximation to the effects which would be produced by a cer- lain savin:$ in fuel, even (lid no alternative exist but that of increasing the size and weight of the engines.

There does not appear to be much doubt about a savi~g in f~zel, even of 40 per cent., being made by eapa~stve worlcing, considering what is now the general average consumption.

If the present ordinary consumption be taken at 4,} lbs. of coal per in- dicated horse-power, a saving of' 40 per cent. would reduce it to ~;lhs. per horse-power, and this quantity will appear ample, when it is consid- ered that many land engines are working with 2~ lbs. per indicated horse- power.

The pressure of steam assumed in the foregoing calculations of the saving of coal, where different sized engines are employed, has been only 20 lbs, above the atmosphere. A very much larger saving would, however, result, if steam of a higher pressure were used. The principle upon which the engines are supposed to be altered, is that of increasing the diameter of an ordinary cylinder, presuming the stroke to remain the same.

As the interests of marine engineers and steam-ship builders must, in the long ru% be identical with those of the merchants or companies em- ploying them, it is clearly of the utmost importance to endeavor by every means to economize fi~el. Little, however, can be hoped for so long as the merchant determinately refuses to pay for that economy in some shape or o~her. It is not to be expected that engineers will supply larger en- gines than custom necessitates, and for which they obtain no additiona[ payment ; nor will they exercise their talents to economize in that di- rection which appears [east appreciated.

Considerable competition has for a long time existed amongst engineers for the purpose of reducing the space occupied by engines, but this has been done without reference to the question of economy in total space of machinery and coal, or without reference to economy in consumption of fuel,

This competition has been~ nevertheless, productive of much good~ From the Load. Mechanics' Meg,, Aug,, 1855.