L. MECHANICS AND ENGINEERING. 493 



of sugar, it is not so great as has been supposed. The ben- 

 eficial action of sugar is, he considers, to be found in the 

 greatly increased solubility of lime in the saccharine solu- 

 tion. While water dissolves only about one tenth of one 

 per cent, of lime, a moderately strong solution of sugar will 

 dissolve as much as three per cent. It is evident that the 

 desiccation of the sugar solution will tend to strengthen 

 mortar by allowing the lime to crystallize. Ultimately the 

 sugar probably becomes converted into carbonic acid and 

 water, which circumstance tends to strengthen the interior 

 of the mortar. In the case of mortar made simply of sand 

 and fat limes, its slight strength is due almost entirely to 

 simple association, and it is destitute of the setting princi- 

 ple possessed by the mortar of soorkee and fat lime. The 

 strongest cement tested by him is that made of soorkee and 

 lime (soorkee being a name given to an artificial puzzuolana 

 made by pounding brick or other forms of burned clay). 

 This cement is at least four times as strong as either pure 

 lime or lime mixed with sand. Its cost is not greater than 

 ordinary mortar, since it can be mixed with twice its volume 

 of sand, and its plastic nature permits of joints being made 

 with it, consuming less than half the quantity which would 

 be used in the case of sand and mortar ; so that it becomes 

 advantageous to use fine bricks that have fairly true surfaces, 

 fitting each other closely. The soorkee cement answers well 

 for plastering ; and, in order to shorten the time required by 

 the soorkee cement to set, a process has been employed by 

 Surgeon Nicholson for preparing the clay in some way which 

 will render it more easily decomposable when mixed with 

 lime. Prof. Papen on Indian Engineering, 1875, 61. 



CONSTRUCTION OF STEEL VESSELS TO RESIST PRESSURE. 



Mr. Walter N. Hill, chemist to the Torpedo Station at 

 Newport, states that in the course of their experiments it 

 has been found necessary tj pay especial attention to the 

 construction of strong vessels for containing liquid carbonic- 

 acid gas. This gas at the temperature of 4 Fahr. exerts a 

 pressure of 322 pounds to the square inch, but at 94 Fahr. 

 its pressure amounts to 1200 pounds to the square inch. 

 The first flasks supplied to the station by Mr. Lay (the in- 

 ventor of the torpedo) were stated to have all been ex- 



