Royal Institution of Great Britain. 457 



Iron, independently of its cheapness and extensive diffusion, is 

 singularly and admirably adapted for the construction of suspen- 

 sion brid«res. When it is considered that the greater part of the 

 weight of these bridges arises from the chains themselves, it is evi- 

 dent that the best material for the purpose is that which has great 

 tenacity with small weight ; and thus we find that iron is at the 

 same time the most tenacious and, excepting tin, the lightest of 

 the common metals. A square inch of good iron requires about 28 

 tons to separate it, and it will not be stretched or otherwise affected 

 with less than half that weight. 



Where, however, economy and portability are important objects, 

 rope bridges will be found advantageous, and they have been 

 during the last few years extensively introduced into British India, 

 by Mr. Shakespear, the postmaster-general at Calcutta. They 

 have produced great benefit in facilitating the transport of troops 

 and baggage, as well as of merchandize and the mails. One of 

 these bridges, 160 feet in length, is so light and portable, that it 

 has been several times set up and removed in a few hours. An 

 interesting account of their construction is given, with illustrative 

 engravings, in the 43rd volume of the Transactions of the Society 

 of Arts ; from whose repository the Institution was furnished with 

 a beautiful model of one of them transniitted from India by Mr. 

 Shakespear. • 



At this meeting several valuable specimens in Natural History 

 were presented by Major-general Hardwicke ; a variety of curious 

 and instructive models of Pumps, of different constructions, were 

 exhibited; as also several new and splendid Literary Publications. 



Friday y March 23rd. 



Mr. Reinagle, of the Royal Academy, delivered a discourse on 

 the beautiful forms derivable from the Oval, and its combinations. 

 We hope, in our next number, to be able, through the kindness of 

 Mr. Reinagle, to give an abstract of his lecture, with illustrative 

 wood-cuts. 



At this meeting, several specimens of Perforated Metallic Plates 

 were upon the table. These were the work of M. Lariviere, and 

 consisted of plates of various metals perforated with circular aper- 

 tures, perfectly regular in their size and arrangement, but of dif- 

 ferent dimensions in different specimens, some of them being of 

 extreme fineness. These holes are formed by punches with flat 

 faces, which, passing through the plates into holes made to receive 



APRIL — JUNE, 1287. 2 H 



