Proceedings of the Polytechnic Association. 699 



Engraving. 

 Dr. P. Yanderweyde explained a comparatively recent metliod of 

 engraving, in which the design is first drawn in ink, of which water- 

 glass is an essential constituent, upon a block formed of such material 

 as to readily absorb the same. The ink hardens the material so that 

 the parts between those to which the ink is applied may be brushed 

 away, so that the design stands out in relief. Inasmuch as the 

 blocks are too soft to be printed from, stereotype plates are formed 

 therefrom, from which in their turn the impressions may be taken. 



UxDEKGROrND EaILWATS. 



The hour for taking up the subject for regular discussion having 

 arrived, Mr. J. K. Fisher read a paper on " Underground Railways," 

 of which the following is a condensation : 



Mr. Fisher described four plans : First, the Metropolitan, in Lon- 

 don ; second, the IS^ew York Underground, assjumed to be the same 

 as the " Central," which is chartered ; third, the Arcade ; and fourth, 

 the inter-street open-cutting plan, by Messrs. Worthen & Schuyler. 



The Loudon "Metropolitan" railway is a fourth in open cuttings 

 and three-fom*ths in tunnels, the tunnels having small openings for 

 ventilation. When running in the tunnels, the steam is exhausted 

 into the tank, the draughts are closed, and combustion is suspended, 

 to avoid contaminating the air ; yet it is complained that the air is 

 oiFensive, causes headaches, stinging sensations in the throat, coughs, 

 and sulphurous taste on the palate ; and two persons had died on the 

 railway ; and the verdict on one, a young woman apparently in good 

 health, was* that her " death was accelerated by the suffocating atmos- 

 phere of the underground railway." 



The New York plan is a tunnel all the way, under streets, with no 

 openings except through hollow lamp-posts fourteen inches in diame- 

 ter, and at the stations. The promoters of this plan expect that 

 these means of ventilation will be suflicient ; that locomotives may 

 exhaust their steam through their cliimneys all the way. 



The Arcade plan is to make a new street under the old one, with 

 sidewalks extending up to the house walls, the ventilation to be 

 through the areas, five feet wide on each side. The promoters -expect 

 that the sub-street will be satisfactorily ventilated and lighted through 

 these areas. 



The inner-street plan is to make an undergj*ade street, as much as 



