124 ANNUAL OF SCIENTIFIC DISCOVERY. 



applied, is in protecting tlic outer walls of buildings, so as to en- 

 able tiiem to resist the action of the weather by making them wa- 

 ter-proof. Through well-built and substantial walls, moisture will 

 make its way, and the ordinary type of dwelling-house is very 

 pervious to wind-driven rain. We recently noticed what INlr. 

 Ransome is doing in preserving stone, and his system of water- 

 proofing is only an application of the same process. 



The external surfaces of tiie walls to be protected are first 

 washed with a silicate of soda or solution of flint, which is applied 

 ajrain and ajrain, until the bricks are saturated, and the silicate 

 ceases to be absorl)ed. The strength of the solution is regulated 

 by the character of the bricks upon which it is to be applied, a 

 heavier mixture being uscid ujion ])orous walls, and a lighter one 

 on those of denser texture. After the silicate has become thor- 

 oughly absorbed, and none is visible upon the surface, a solution 

 of chloride of calcium is applied, which, immediately combining 

 with the silicate of soda, forms a perfectl}' insoluble compound, 

 which completely tills up all the interstices in the brick or stone, 

 without in any way altering its original appearance. By this op- 

 eration the wall is rendered perfectly water-tight, and, as the 

 pores of the bricks are thoroughly filled for a considerable depth 

 from the surface with the insoluble compound, which is entirely 

 unaffected b}' atmospheric influences, no subsequent process is 

 necessary. 



Already Mr. Ransome has successfully applied this process to 

 a large nujuber of buildings, several of which were previously 

 almost uninliabitable from the constant dampness, and a length- 

 ened experience has proved that it is not only thoroughly effect- 

 ive ; but, from the comparative insignificance of its original cost, 

 and the fact that renewals are never required, the system recom- 

 mends itself for general adoption in preference to all other methods 

 of water-proofing. 



THE NEW MODE OF FIRING GUN-COTTON. 



An interesting practical exhibition of the newly discovered 

 properties of gun-cotton when fired l)y concussion, instead of by 

 the direct application of flame or heat, was afforded recently at 

 Woolwich. The huge 36-inch I\Iallet mortar, weighing 52 tons, 

 which was placed in the marshes in 1857, and dcsignetl to fire a 

 shell 2,548 lbs. (empty), has, for some lime past, been sinking in 

 its great wooden bed, owing to the gradual decay of the wood. 

 It was thought dangerous to run the risk of its lalling uptm any 

 visitor by leaving it in this position. But weights of 52 tons can- 

 not be moved for nothing. To erect sheers and the necessary 

 appliances for raising the mortar would h ive entailetl an ex- 

 penditure estimated at about 50 pounds. Under these circum- 

 stances, recourse was had to gun-cotton to destroy the bed, and 

 precipitate the fall of the mortar. Four charges of 4 ozs. each, 

 4 of 6 ozs., and one of 8 ozs. (total, 48 ozs.), were ]daced on the 

 wooden bed, and exploded by means of mining fuses charged 



