56 ANNUAL OF SCIENTIFIC DISCOVERY. 



far served its purpose, without a resort to this apparatus. The structure is 

 thus described : 



It consists of an iron cylinder 37 feet in diameter and 85 in height, 

 containing* within itself all the arrangements of air chambers, passages, 

 etc., necessary for using it either as a large diving-bell or simply as a coffer 

 dam, as circumstances might require, and so constructed as to be afterwards 

 divided into two parts vertically, and removed after the pier shall have 

 been built within it. The whole, weighing upwards of three hundred 

 tons, was safely launched and floated into place, where it was raised per- 

 pendicularly, and pitched upon its lower edge in the centre of the river. 

 The river is at this point upwards of 50 feet deep at low water of neap 

 tides, and except for a short space on the turn of the tide, there is a con- 

 siderable current ; under such circumstances, this cylinder, drawing 50 

 feet of water, was pitched upon its lower edge accurately that is, within 

 three or four inches of the exact point required. Since then the work has 

 been carried on at the bottom of the cylinder, as in a diving-bell, against 

 a pressure of water occasionally of 70 and 80 feet. The mud and other 

 deposits forming the bed of the river for 10 feet or 12 i'eet in thickness, 

 have been removed, and the cylinder is now resting on the rock, and pre- 

 parations are making for excavating the rock into level beds for receiving 

 the masonry. 



ACTION OF SEA-WATER ON CEMENTS. 



M. M. Malaguti andDurocher, have lately devoted much attention to 

 the action of -sea-water on hydraulic cements, and have discovered that 

 " Parker's," which contains a considerable portion of the oxide of iron, 

 stands the best. They formed several kinds of puzzolanas by making 

 mixtures of silica and a little lime with alumina and oxide of iron, and 

 tien studied the action of sea- water on these mixtures, previously heated to 

 a dull redness. After immersion for some time, these substances augmented 

 in volume, and possessed the most remarkable characters. Each of them 

 divided itself into two distinct compounds, one of which attached itself to 

 the bottom of the flask, and had gained considerable cohesion and adher- 

 ence ; whilst the other assumed a flocculent aspect ; it swelled out more and 

 more, and rose above the bottom. In analyzing these different com- 

 pounds, they have found that the quantity of lime precipitated is inde- 

 pendent of the presence of alumina, whilst it is augmented by the pres- 

 ence of oxide of iron. Further, they have recognized that the flocculent 

 compound was the richest in alumina, and that the concreted deposit was 

 richest in oxide of iron. 



These synthetical experiments having apparently demonstrated that oxide 

 of iron is not an inert constitutent of hydraulic cements ; they believe that 

 the presence of this oxide would contribute to give stability to mortars and 

 cements immersed in sea- water. It remains, however, to be ascertained 

 whether cements or artificial hydraulic limes, formed by the addition of 



