TRANSACTIONS OF THE SECTIONS. 155 



On Steam Cultivation, Bif Dayid Greig. 



On the Heating of Hot Houses. By John Hallidat. 



On an Improved Suspension Bridge. B>j A. S. Hallidie, C.E. 



On the Application of Machinery to Boring and Tunnelling. 

 By General Haupt. 

 The autlior gave an account of the circiunstanees under which he had been led 

 to consider the possibility of applying steam to tunnelling, an application which 

 engineers had universally pronounced impracticable, but which he had demonstrated 

 to be not only possible, but, under certain circumstances, highly advantageous. 

 The author then explained the construction of his driUing-engine, the mode of 

 mounting, the appliances for erecting and removing tlie machines, the power to 

 drive them, the questions of ventilation, lighting, blasting by electricity, and the 

 application of the system to Cornish mining. Tlie construction of the' machines 

 was explained by means of diagrams, without which it would be hopeless to attempt 

 a description. On the subject of power, the author discussed the question of com- 

 pressed air, the loss of power in compression and transmission, the possibility of 

 using steam by the aid of a vacuum-pipe, the superiority of the ventilation, &c. 

 From experiments made by the author at the Franklin tunnel, the enormous loss 

 of power by passage of air through pipes has been practically measured. As an 

 instance of the advantage of using large pipes, it was stated' by General Haupt 

 that with 110 square inches of cross-section, 550 horse-power would be required 

 to pass 3674 cubic feet of air per minute through a pipe four miles long, whereas 

 less than ten horse-power would suffice if the pipe had a cross-section of ten square 

 feet. In the course of the reading of the paper. General Haupt alluded to the mili- 

 tary railway bridges constructed during the civil war in America, and he explained 

 the system by diagrams on the blackboard, and showed how a bridge had been 

 constructed in four days and a half, chiefly by the aid of negroes, which was 600 

 feet long, and nearly 100 feet high, the timber being cut from the stump. 



On the Iron and Steel at the Paris Exhibition. By Ferdinand Kohn, 

 The collection of iron and steel in the Paris Exhibition was one of the most com- 

 plete and instructive representations of the present state of iron metallurgy in 

 aU its branches which could have been brought together at any one spot under any 

 circumstances. The wi-iter then spoke of the main cause of the gi-eat industrial 

 revolution now witnessed — an invention with which the British Association had an 

 historical connexion — the Bessemer process, which process had been most suc- 

 cessfid dm-ing the eleven years of its existence. He next referred to those much- 

 admired steel castings of Khenish Prussia, which had caused st) much interest and 

 curiosity by their extraordinary sizes and qualities, and he referred to the secrecy 

 and mystiti'cation which surrounded their manufacture, arising, in his opinion, from 

 the want of an effective patent lawiu Prussia. In conclusion, he remarked that 

 the vague notion now existing in Britain that the superiority and predominance of 

 British iron manufacture had ceased to exist, or was threatened to be overthrown 

 by continental competitors, had no fomidation, judging by tlie state of things in 

 the Palis Exhibition. 



On an Improved Marine Steam-Boiler. By J. Lewisi. 

 This boiler is constructed with a series of undulating flues, instead of the or- 

 dinary arrangements of tubes employed in marine Ijoilers. The results of a series of 

 experiments made with marine boilers of this construction show a very considerable 

 economy in the quantity of fuel rec[uired, and also the evaporation of a given C|uan- 

 tity of water in a given time. This boiler occupies the same space, and is ex- 

 teiTially of the same form, as the ordinary tubular boiler. 



