160 
REPORT—1854. 
It is shown that Stirling's air-engine, as compared with a theoretically perfect 
air-engine, wasted two-thirds of its fuel, and Ericsson's somewhat more. 
Two obvious and powerful causes of that waste of fuel are traced,— 
1. Deficiency in extent of heating surface ; 
2. The communication of heat from the furnace to the working air, at those 
periods of the stroke when it is not performing work. 
The necessary conclusion is, that the more completely we remove those two causes 
of waste of fuel, the more nearly shall we approximate to the theoretical extent of 
the oecanomy of the air-engine, an extent far exceeding that to which the economy 
of the steam-engine is restricted; and the more fully, in short, shall we accomplish 
that which has hithertobeeq vwv imperfectly done; »>. iirai.izk Ttltc advantages 
or run air-engine. [These first three sections have been published in the Edin¬ 
burgh Philosophical Journal for January 1855.] 
^ I he fourth sectiun describes the improved nir-engine of Messrs. James Robert 
Napier and W. J. Macquorn Ranking, in this engine the heating surface is in¬ 
creased to any required extent by means of tubes employed in a peculiar manner, 
ihc waste ol heat, from its communication to the air at improper periods of the 
stroke, is prevented hy a sort of plunger, or combination of plungers, called the 
Heat -screen, which prevents any access of the air to the heating surface, except 
when it is in the act of expauding, and ao performing work. The engine may be 
made ol the same size with a steam-engine of the same power, or smaller, according 
to the degree of condensation at which the air it employed. 
Independently ot the amount, and value of the saving of fuel which will result 
from the introduction of the air-engine, it possesses the important and incontestable 
advantage, that even should an ut- receiver burst (which is very unlikely), the ex¬ 
plosion would be harmless, for its force would not be felt beyond the limits of the 
engine itselt, and hot air does uot scald 
Rbi ® presented a sketch of the plan of ventilating St. George’s Ilall; and 
at the conclusion of the sitting he accompanied the members over the building to 
show the arrangements. 
On 
"\r'r l , '°y rc( ' s pf Naval Architecture and Steam Navigation, including& 
notice of the large Ship of the Eastern. Steam Navigation Company. M 
John Scott Russell, C.E., F.Il.S. 
Ru . ssc11 ^plained the elementary principles which guide the construction of 
slaps, and condemned the legislative restrictions which, till within the last twenty 
?PJ l,ira *i°n "f those principles. The old " sea chests/’ "Inch 
S M r lh a vicw to RV0itl the taxation imposed on ships that were no 
xvindwnrHn«» ain *l ,a P w ' posseted neither the requisite properties of stability 
r d r Wre w 7’ * ,ow 5 Ihcy were built solely with a View to hold the 
nullities of n CR | rfit ' Wllb ' n u K‘ v en superficies, without regard to the oth 
building fnr j!!!?' ,n M “ n Kling and piratical vessels the true principle of »b»P 
.... . i°’ qumng speed, had however been long introduced before the su d 
Hnh,™ P . b . y .- h , C ?T' sh A "ociati«n. and the wave principle of construction had 
r ,neo n e ? ab U, r d 7 on a large scale. A fi»* c 
Uir rounU how. is now generally admitted to be the b«t. 
bodv nf n ! n r he #1,a P e the water line, it had hern found that length of the 
for the nnr?i h J *7 ?***? '> P****g' through the water, by allowing a longer one 
Sdv ,he 101,1 to ^parate. A ship with a tine concave bow. a log 
the water IS, 1 ?” 1 ** y rMod stern, Mr. Russell said, cleaves its passage thro'g 
nUs notTftir T ,‘ U * Wg a wave in front to obstruct its course. No stcam_ h l 
a creat exnoml,^' T 111,1 bc P ro P*»^ at a speed of sixteen miles an hour with® 
fa£3«fto he ; i : ,ul 100 fret is the shortest length for a ship that i 
illustration of tv ‘. at ^tgll a speed as twenty-four miles au hour. 
onTat^n^h^ [“K" Wtt3 »n«*tio«id that the ‘Himalaya/ which » 365 flg 
long, attains the greatest speed for the power employed of anv merchant ship- J 
"T l ‘ 0TO ™! the bu’Kwm met’ with the 
not being able to find wood of sufficient size for the requisite strength, since no 
