Mathematics and General Physics, 407 



SUB-SECTION. 



M. I. Brunei, Esq. in the Chair. 



Mr Dent exhibited a chronometer with a glass balance-spring, 

 and presented an account of its rate kept at the Royal Observatory, 

 Greenwich, since the last meeting of the Association. He also 

 shewed a chronometer in motion, with a pure palladium balance- 

 spring, a table of the variations of gold, steel, palladium, and glass, 

 from 32° to 100° Fahr. ; and another table shewing the qnantities 

 respectively due to direct expansion, and to loss by elasticity in 

 steel and palladium. 



Mr Adam gave a description of a Sextant Telescope of his in- 

 vention, furnished with a spirit level attached to its eye-tube, for 

 taking vertical angles or altitudes on sea or land, when the horizon 

 is invisible- 

 Mr Ramage read a proposal for constructing a reflecting teles- 

 cope, of greater magnitude than has yet been attempted, and exhi- 

 bited a model of the proposed instrument. Mr Cooper stated, that a 

 superior reflecting telescope had been constructed by Mr Grobe of 

 Dublin, at one-fifth of the usual cost, and expressed his perfect con- 

 fidence in the ultimate success of the invention. 



Mr Alexander Gordon exhibited Muretz's modification of Fres- 

 nel's polyzonal lens, which (with a common Argand flame*) Mr Gor- 

 don proposes as an economical light for ports and harbours; and to 

 be adopted when a more intense flame is used for coast light-houses, 

 in situations where the use of parabolic reflectors is not absolute- 

 ly necessary. 



Skction B. — Chemistry and Mineralogy. 



The Chemical Section met at 11 a.m. 



Mr West gave an account of his experiments on bar iron, shew- 

 ing that when dissolved in muriatic acid, sulphuretted hydrogen is 

 given ofl' from bar iron of the best quality. He inferred that sulphur 

 is present as a deteriorating substance in most malleable irons ; and 

 he suggested that the quantity of sulphur in such irons should be 

 determined more accurately. On the mode of ascertaining this 

 point, some discussion arose. 



A notice by Sir David Brewster was then read regarding a large 

 specimen of amber from Ava, intersected by thin layers of carbon- 

 ate of lime. 



