TRANSACTIONS OF THE SECTIONS, 237 



if possible, all refuse matter except the smdl ashes from the fire, and securing that 

 these ashes shall be placed upon the excrement daily. In every case the ash-pit is 



E laced as far from the entrance-door of the house as possible ; and as in all new 

 ouses a yard-space of considerable size is required, generally the privy and ash-pit 

 Avill not join up to the walls of the house, and in every case where it does so a 

 strong flag is placed between the wall and the privy ; and as the floor is sunk be- 

 neath the level of the floor of the dwelling, percolation wiU be entirely prevented. 

 In addition, a ventilating-shaft must be carried up to the eaves of the house, the 

 horizontal portion of which may form the coping of the separating wall between 

 the two houses, and the area of this shaft must not be less than eighty-one square 

 inches. A drain and grid are also required in the yard to carry ott" tlie water and 

 slops of the house into the street sewers. Already upwards of 1500 have been 

 erected under the supervision of the committee ; the occupants are perfectly satis- 

 fled, and are constantly expressing their approval. The opposition of the property 

 owners is subsiding ; and although it will take many years to alter and improve 

 the 30,000 old ones in the city, the committee . and the officer of health feel confi- 

 dent that every step in this direction will tend to reduce the death rate and improve 

 the health of the inhabitants! " 



Pneumatic Disjmkli. — On Pneumatic Transmission tlirough Tunnels andPipes*. 



By Egbert Sabine. 



The author, after giving the residt of investigations into the motions of bodies 

 through tubes for this purpose, and the formulas which he had arrived at, said that 

 these would show that small pneumatic tubes could be worked more advantage- 

 ously than large ones. The great convenience of and practical facilities for work- 

 ing small letter-carrying tubes have been amply proved by the extensive systems 

 already laid down, in Paris, Berlin, London, and in other towns, as adjuncts to 

 the telegTaph services. Tubes of somewhat larger diameter, such as those pro- 

 posed some years ago "by Mr. A. E. Cowper for the more speedy distribution of 

 metropolitan letters to the branch post-ofiices, would undoubtedly work satisfac- 

 torily. Even still larger tubes, if of moderate lengths, might also be found useful 

 for a variety of special applications ; for instance, in the transport of light materials 

 between the different parts of a factory supplied with steam-power. lie did not 

 believe that a pneumatic line working through a long tunnel could, for passenger- 

 traffic, ever compete in point of economy with locomotive railways. A pneumatic 

 railway is essentially a rope railway. Its rope is elastic, it is true, but it is not 

 light. Every yard run of it, in a tunnel large enough to carry passengers, would 

 weigh more than J cwt. And a rope, too, which has to be moved against con- 

 siderable friction, in being compressed and moved wastes power by its liberation 

 of heat._ In a pneumatic tunnel, such as that proposed between England and 

 France, in_ order to move a goods- train of 250 tons through at the rate of 25 miles 

 an hour, it would be necessary to employ simultaneously a pressure of 1^ lb. per 

 square inch at one end, and a vacuum of I a lb. per square inch at the other. The 

 mechanical effect obtained with these combined (pressure and vacuum) would be 

 consumed as foUows : — 



In accelerating the air 29 ) 



In accelerating the train .... 12 / millions of 



By friction of the air 6721 ( foot-pounds. 



By friction of the train 330 j 



The resistance of the air, therefore, upon the walls of the tunnel Would alone 

 amount to 93 per cent, of the total mechanical effect employable for the transmis- 

 sion, while the really useful work would be only about SJ per cent, of it. And to 

 compress and exhaust the air to supply the above items of expenditure of mecha- 

 nical eflPect, engines would have to exert over 2000 horse-power at each end during 

 the transmission, even on the supposition that the blowing'-machinery returned 

 an equivalent of mechanical effect such as has never yet been obtained. This 



* Published in extenso in ' Engineering,' Sept. 23, 1870. 



15* 



