L. MECHANICS AND ENGINEERING. 475 



more recent strata. These are estimated at not less than 

 56,273,000,000, making an aggregate of 146,480,000,000 tons 

 as the amount available in the British Islands. Assuming 

 that the present rate of consumption 115,000,000 tons re- 

 main constant, this amount of coal will last 1273 years. But 

 should the rate of consumption increase as predicted by Pro- 

 fessor Jevons, the supply will be exhausted in 110 years. 

 Applying, however, a reasonable correction to Professor Je- 

 vons's estimate, it is thought that the quantity mentioned 

 will last for 276 years. 16.4, October, 1871, 538. 



FURNACE SLAG FOR ROAD BALLAST. 



The journal of the Franklin Institute mentions a method 

 of utilizing slag, as used at the blast furnaces at Osnabriick, 

 which consists in allowing it to fall into a stream of water 

 from a height of about eight feet. By this means it becomes 

 granulated into particles of the size of beans, and it is then 

 used as ballast for roads and railways. 1 D, March, 1872,160. 



TOMMASl's FLUX MOTOR. 



We have already noticed in a previous article the inven- 

 tion by Tommasi of what he calls the flux motor, being a sys- 

 tem of machinery for utilizing the ebb and flow of the tide 

 as a mechanical agent. As at first constructed, it could only 

 be brought into play in quite a limited number of localities ; 

 but we now learn that, by a recent modification, the appa- 

 ratus has been made of a more practical character, and that, 

 whether with a rising or an ebbing sea, the piston of the ma- 

 chine will always work under a pressure equal to the weight 

 represented by a column of sea-water the height of which is 

 the same as the total depth of the sea at that place. As a 

 depth of sea of about thirty feet represents nearly the weight 

 of one atmosphere, this amount of pressure can now be ob- 

 tained at almost any part of the sea-coast without difficulty, 

 so as to have the flux motor act without any interruption. 

 3 B, November 9, 1871, xxvtil, 341. 



RUPTURE OF IRON WIRE BY A BLOW. 



As the result of a series of investigations upon the rupture 

 of iron wire by a blow, Mr. John Hopkinson comes to the fol- 

 lowing conclusions : 



& 



