Report on the Trade in Animals. 
235 
ever, the wind is ahead, it tends to drive the exhausted air back 
into the hokl, and further acts as a shut valve to prevent its 
escape.* Similarly, the downcast air has to overcome the resist- 
ance of a column of heated air which is naturally ascending, 
and, as it were, trying to escape through the tube of the windsail. 
These defects, however, can be easily controlled by mechanical 
means ; and as it does not appear that contrivances for this pur- 
pose are generally known, 1 have thought it advisable to give a 
section of a metal windsail or ventilator, furnished with an upcast 
as well as a downcast arrangement, so as to remove the last-men- 
tioned obstruction to the column of fresh air ; and also of one of 
the machines known as blast ventilators, which are worked by a 
small steam-pipe from the ship's boiler. 
The first of these arrangements does not require any further 
explanation ; and of the second, it will be sufficient to state that 
the steam from the boiler entering the small steam-pipe shown 
in Fig. 5, and impinging against a wheel having transverse pro- 
jecting ridges on its circumference, drives it round as water does 
an ordinary water-wheel. The shaft from this wheel is connected 
with a fan (shown in the upper part of the figure) which drives fresh 
air into the hold, acting like the blower of a winnowing machine. 
The manufacturers (the Co-operative Ironworks Company, North- 
moor Foundry, Oldham j) have informed me that such an appa- 
ratus, capable of injecting 350 cubic feet of air per minute, costs 
only 15/. 10s. Larger sizes cost more money, but are nevertheless 
relatively cheaper, in comparison with their power, so that a 
machine capable of pumping into the hold 4500 cubic feet of air 
per minute does not cost more than 55/. 10s. Under these cir- 
cumstances, it appears to me that all cattle-boats should be 
furnished with machine ventilators of such a power that the 
ventilation of their holds should be both adequate and uniform, 
without being dependent on variations in the force and direction 
of the wind, the state of the tide, or the speed of the steamboat. 
That there is no practical difficulty in the way of ventilating 
the cattle-holds by mechanical means is sufficiently proved by 
the fact that some of the steamboats belonging to the City of 
Dublin Steamboat Company and the North German Lloyd are 
* Mx. Walters has also noticed this fact in the ' Food Journal,' vol. iii. p. 469. 
That gentleman, however, seems to infer that the lower holds are the worst 
ventilated ; but a consideration of the various circumstances affecting the ventila- 
tion of steamboats ouglit to be sufficient to show, on the contrary, that, in a steamboat 
having several cattle-holds, tlie best ventilated one is, cxteris paribi(S, the lowest, 
because there is tlie greatest difference in the relative weights of the upcast and 
downcast columns of air having access to it. 
t ilachines for, I believe, drawing off foul air are manufactured bj' the Union 
Engineering Company, 2, Clarence Buildings. Booth Street, IMiuichcster ; but I 
have not received a section of one in time for publication. 
VOL. IX. — S. S. R 
