SCIENTIFIC SUMMARY. 
465 
anywhere in the neighbourhood of London, where the atmosphere is suffi- 
ciently pure, and obtain his water direct and uncontaminated from the 
clouds. 
Dynamical Transmission of Power . — Of all the recent mechanical inven- 
tions exhibited at Paris, probably none is destined to more important appli- 
cations, or has required a greater amount of practical skill in its development, 
than the system for the transmission of motive power to great distances, by 
means of bands of endless wire rope, exhibited by M. Hiru. The single 
novelty of principle, if such it can be termed, is the substitution of velocity 
for weight in the rope ; but the devices by which the system is carried out, 
so a3 to obviate losses of power on the one hand, and injurious wear on the 
other, are of the highest merit. For transmitting 120 h.p., M. Hiru adopts 
a rope only 0*4 inches diameter, passing over pulleys 13 or 14 feet diameter, 
and making 100 revolutions per minute. With these proportions, inter- 
mediate supports are not required for less distances than 160 yards. He 
estimates the loss of power in transmitting 120 h.p. a distance of 12 miles 
at only 21 h.p. The system has received considerable development in 
France, having been applied already in 400 instances. An interesting account 
of the invention will be found in Engineering for June 14. 
Rifled Small Arms. — The Government have now experimented upon up- 
wards of 80 breech-loading rifles, sent in for competition with the Snider 
gun. In the trials for rapidity of fire, the time required to discharge at a 
target 12 rounds of ammunition varied from 39 seconds (Soper rifle, with 
Boxer cartridge) to 123 seconds. 
Gunpowder Magazines. — In reply to the Commission, appointed by Govern- 
ment after the Erith explosion in 1864, to report on the measures which 
ought to be taken for the safe storage of gunpowder in magazines, Mr. Mallet 
has written a most interesting letter on the effects of the explosion of large 
masses of gunpowder, and on the laws of the propagation of the aerial and 
earth waves which carry destruction to neighbouring objects. The letter 
will be found in the Engineer of June 14. Mr. Mallet does not think that 
great destruction is likely to be caused by the elastic wave of shock propa- 
gated through the earth, except within a very limited area round the focus. 
To protect the surrounding country from the effects of the aerial wave, he 
suggests the construction of a large permanent traverse or bank, in the 
shadow of which surrounding objects would be secure from the direct action 
of the aerial wave. In order that this traverse may stand, it must be with- 
out the sphere of explosion, within which the effect of the explosion is to 
form a paraboloidal crater in the earth on whose surface it is exploded. The 
inner slope should have an inclination fixed by the asymptotes of the curve 
representing the section of the excavated crater. In fact, the magazine should 
stand in the centre of a conic frustum, or etonnoir. 
Hot Air Engine. — An interesting and novel form of air-engine, exhibited 
by Mr. Shaw at Paris, has been experimented upon with the following 
results : — 
Duration of experiment, 7 hours. 
Average work (indicated), 22 h.p. 
Total fuel used (deducting 20 lbs. remaining unburnt, and 18 lbs. wood 
for lighting), 222 lbs. 
Average quantity of fuel per h.p. per hour, l # 41bs. 
