800 REPORT — 1886. 



carried out without difBcuIty. The author proceeded to give au account of the 

 manner iu which the process is carried out, by passing a freezing liquid down 

 numerous bore-holes surrounding the ground to be excavated. After the freezing 

 has been effected, the excavations are commenced and secured in the ordinary 

 manner. 



Several shafts through water-bearing strata, extending to a depth as great as 

 76 metres (250 feet), are enumerated as having been sunk in this manner ; the cold 

 is usually obtained by means of a Kroppf s (Carr(5) ammonia machine. The system 

 is readily applicable in bridge-construction, and will at times obviate the necessity 

 of using very large spans. 



After discussing many practical points in regard to the application of the 

 system, the author considered the question of cost, and gave a mathematical inves- 

 tigation of the cooling effect and time required for the operation, &c. Calculation 

 shows that, to take an imaginary case, the freezing of the ground to sink a pier 

 60 metres below water-level, and 40 metres below the river-bed, and having a base 

 18 by 8 metres, would occupy 2,250 hours and require a cooling effect equivalent 

 to 2,230 cubic metres (or tons approximately) of ice. About 2,900 cubic metres of 

 ground would be frozen in the operation, the wall attaining a mean thickness of 

 2 metres. 



4. On the Laffitie Process of Welding Metals. 

 By William Anderson, M.Inst.G.E. 



The author pointed out that in order to make a sound weld it is necessary that 

 the surface of iron be free from oxide, and that the usual mode of approximating to 

 this condition is to heat to the ' welding ' heat — about 2,800° F. Such a high 

 temperature, however, impairs the quality of iron and, to a far greater extent, of 

 steel. Many qualities of steel cannot be welded. 



In order to overcome these difficulties, powders, with borax as a basis, are 

 generally employed. 



With a view to overcome the difficulties experienced in spreading these 

 powders evenly over surfaces, often irregular and of considerable extent, 

 M, Laffitte has invented plates, usually consisting of very pliable wire gauze, on 

 both sides of which the flux, being vitrifipd, is evenly spread. Paper may also be 

 used as a support, and in the case of small surfaces it is often sufficient to form a 

 sheet of the flux and metal filings agglomerated together. 



After describing the method of preparing these plates and various modes of 

 applying them, the author mentioned that they have a very extensive use in France 

 for all branches of metal work, including fancy iron-work, and in the arsenals, 

 gun factories, and on the railways, &c. 



Tables were given showing the satisfactory results of severe tests made both in 

 this country and on the Continent. 



FRIDAY, SEPTEMBER 3. 



The following Papers were read : — 



1. Furnaces for the Manufacture of Glass and Steel on tlie Open-hearth} 



% John 'Head, F.G.8. 



The author first referred to the simple furnaces formerly used in the manufacture 

 of glass and iron, to the special facilities of Birmingham in the possession of clay 

 beds, iron and coal mines, as a manufacturing centre, and to the surrounding dis- 



* Published in extenso in Industrieg, September 1886. 



