MECHANICS AND USEPUL ARTS. Gl 



In a report made on its probable stability, Professor Rankine 

 says : " From previous experiments on the strength of the bricks 

 used in the chimney, I consider that their average resistance to crush- 

 ing is ninety tons per square foot. I calculate that, at the level of the 

 ground, the pressure on the bricks arising from the weight of the chim- 

 ney will be about nine tons per square foot, or one-tenth of the crush- 

 ing pressure. I consider that, in violent storms, the pressure on the 

 bricks at the leeward side of the chimney may sometimes be increased 

 to about fifteen tons per square foot, or one-sixth of the crushing force. 

 On these grounds, I am of opinion that the chimney, if executed as de- 

 signed, will be safe against injury by crushing of the bricks." On the 

 9 tfii of September, 18J9, however, afte* a hurried construction, a vio- 

 lent storm swayed it from the perpendicular, the deflection produced 

 extending to seven feet nine inches. On the 21st of the same month, 

 and subsequent days, it was restored to the perpendicular by twelve 

 separate sawcuts, as recommended by Mr. I). Macfarlane, architect, 

 who afterwards reported, as did Mr. Rankine, that it was then per- 

 fectly safe. The highest cut was one hundred and twenty-eight feet 

 from the top, and the least distance between any two cuts was 

 twelve feet. 



A SUBSTITUE FOR EXTERNAL CHTMNEYS. 



M. M. De Janges and Masson, in a communication made recently 

 to the French Academy of Sciences, have shown how external chim- 

 neys may be dispensed with. They propose that the upper aper- 

 tures of all the chimneys of a house should be received into a cham- 

 ber at the highest part of the edifice, whence the smoke shall escape 

 by one aperture only. They also propose that the hot vapor shall 

 be utilized in various ways. M. De Janges enumerates among 

 the advantages of his system, which has been tried at Neuilly, 

 that the draught in the chimneys is constant and equal, that confla- 

 grations may be more easily extinguished, and that fifty per cent, is 

 saved of the cost of removing soot. 



RUNAWAY HORSES -A NEW CHECK. 



A great many patents have been taken out of late years for stop- 

 ping runaway horses, and in almost every saddler's shop we see 

 engravings of apparatus devised to squeeze a horse's throat, or nose, 

 or to catch up one leg and throw him down. But to all this ma- 

 chinery it is objected that if a horse is really running away at a 

 great pace he cannot be stopped suddenly by violent means with- 

 out considerable risk both to man and beast. A very ingenious 

 invention, operating upon the horse's movements by moral force 

 alone, has been recently brought out by M. Leveque, a "French officer 

 of the Cavalry School of Sauniur. His plan will assuredly not be ap- 

 proved of by those who object altogether to the use of blinkers, for 

 it is but an extension of the blinker system. The partisans of blink- 

 ers, however, for horses in harness, are, up to the present time, in an 

 enormous majority. 



The leading idea of M. Leveque's invention is to induce the horse 

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