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vertical depth of disturbance corresponding to the ascertained velocity of 
these waves, and he finds it to correspond nearly with the mean depth of 
the vessels. 
British Association Meeting at Nonuich. — Amongst the papers read before 
the Mechanical Section, we may ipention one on Centrifugal Pumps by 
Messrs. J. & H, Gwynne ; one by Mr. L. E. Fletcher, C.E., on Boiler 
Explosions and Coroners’ Inquests ; one on the Utilisation of Convict Labour, 
particularly with reference to the application of the motive power to tread- 
wheels, on which hard labour sentences are generally worked out, to weav- 
ing, by Mr. Appleby ; a paper on the Norfolk Broads, as a source of water 
storage and supply, and with reference to the improvement of the land in 
their neighbourhood by drainage ; and a paper on the means in use and pro- 
posed to be used for the Irrigation of Lombardy, by Mr. P. le Neve Foster. 
Mr. Whitworth also returned to the subject of flat -fronted projectiles, which 
he first invented, and which (in spite of Major Palliser’s successes) he still 
elieves to be in many cases superior to any other form in penetrative power, 
and to be alone capable of entering and passing through water. 
Boiler Explosions . — Mr. L. E. Fletcher asserts that the experience of the 
Manchester Association for the prevention of these accidents proves that they 
arise from the simplest causes, and are perfectly within the grasp of common 
knowledge and common care to prevent. He gives some remarkable in- 
stances of the unscientific and absurd evidence sometimes given and accepted 
at coroners’ inquests, and recommends a more adequate investigation by 
competent scientific engineers in all cases of fatal boiler explosions — the 
accoimt of the enquiry, with the engineers’ reports, being printed and 
deposited in the Patent Office. He believes that this course would do more 
to prevent accidents and be less objectionable than the Governmental inspec- 
tion of boilers so often recommended by j uries. 
Eynamite. — M. Nobel read a paper at Norwich on Dynamite, the name 
given to an explosive material intended for mining purposes. It consists 
simply of 75 per cent, of nitro-glycerine mixed with and absorbed by 25 per 
cent, of highly porous silica. The mixture renders the nitro-glycerine solid 
or pasty, and does not in any other way affect its properties. But if M. 
Nobel’s opinion be correct, that the danger of nitro-glycerine is due almost 
exclusively to its liquid form, this improvement in the mode of using it is 
most important. M. Nobel exhibited a block of wrought iron, II inches 
diameter and 12 inches high, rent in two by a charge of only 6 ounces of 
dynamite, simply placed in a bore-hole at the centre, without any plug or 
tamping. To prove its safety, he mentioned that a box containing 8 lbs. 
(equal to 80 lbs of gunpowder) placed over a fire, slowly burned away with- 
out explosion, and that a box containing the same quantity had been dropped 
60 feet on to a rock without igniting by concussion. 
Path of Projectiles. — Mr. Memfield has investigated the form of the path 
of a projectile, on the assumption that the resistance, as shown by Professor 
Bashforth, varies as the cube of the velocity. He finds the path to bear a 
rough resemblance to one branch of an hyperbola, with one of its asymptotes 
vertical. — See Engineer for August 21. 
Moncrieff Gun Carriage . — This remarkable and novel arrangement of gun 
carriage has just been tried at Shoebuiyness, in presence of the Ordnance 
