496 TRANSACTIONS OF THE 



The auroras have been considered by several writers Leretofore, as 

 attaining heights far above our atmosphere. 



Marian calculated one at 525 miles, Bergman one at 4G0 miles, and 

 Euler at several thousand miles, &c. Henry Meigs. 



September 16, 1859. 



THE world's telegraph. 



The Club (Polytechnic) proposed the route by Behring's Straits before 

 the Atlantic cable was laid and lost. One member, Mr. Tillman, said, 

 and so said others, that our knowledge of electricity did not warrant' so 

 long a line of induction, especially at ocean depth ; that, even- if successful, 

 it would uot accommodate the millions who want it as post ; that Behring's 

 Straits would accommodate thousands of wires, the depth being but 200 

 feet, and the length, in all, about 50 miles, divided by the islands Ratman- 

 oiF, Kruzcnstein, and a Rode ; that, as it was a common cause of nations; 

 the Czar of Russia would do it, and all nations join in its maintenance. 

 The plan is already laid for a line along the great river Amoor, over 2,000 

 miles, to Ochotsk, and thence to the IJast Cape. That is the only path, 

 because the liability to get out of repair makes it indispensable to have- 

 it within easy reach. This plain road can be made and kept, and no 

 necessity for burning the City Hall to illustrate it. 



The above plan is published in the transactions of the American Institute 

 about two years ago. H. Meigs. 



NovemLer'21, 1859. 



[Ingenieur Vereines, Vienna, July, 1859.] 

 BRIDGES. 



The last numbers of the transactions of the Union Engineers of Austria, 

 contain among other valuable scientific matter, drawing and description of 

 a new stone bridge over the rapid river Sann, formed of arches, based on 

 the rock under it, and the whole bridge huilt on an arc convex to the 

 stream. 



The communication on the telegraph called forth some remarks from Mr. 

 Seeley, in which he attributed the failure of the " cable " partly to the use of 

 iron-wire around the copper core, the two metals and the gutta percha 

 between forming a sort of Leyden jar arrangement, and partly to the em- 

 ployment of gutta percha, instead of india-rnbber, as an insulator. 



Mr. Garvey remarked upon the bridge alluded to, that the employment 

 of an inverted arch, to prevent the sinking of buildings in soft ground was 

 common — the arch distributing the load over a large surface, so that no 

 part was under more pressure than it could well support ; but he never 

 before heard of a bridge being built with an inverted arch to prevent 

 its being blown up by a flood. There could be no difficulty in constructing 

 a bridge of one or several arches, formed in the usual manner, and a coun- 

 ter inverted arch spanning the whole length of the bridge, to keep the 



