418 Proceedings of the Society of Arts. 



the piston rod is carried up and down in a straight line, which is mathe- 

 matically correct ; while, by the method of Watt, the piston rod is never 

 at any one point carried in an absolutely straight line, and at top and 

 bottom of the stroke it is very considerably deflected from the straight 

 line, which gives rise to much friction and strain on the mechanism. 



4. A short notice on the Constitution of Steel. By Samuel Brown 

 junior, Esq., Haddington. Communicated by Mr Alexander Bryson, 

 M.S. A. (628.) Thanks voted, and referred to the Experimental Com- 

 mittee. 



This paper was intended to draw the notice of the Society to the ques- 

 tion whether steel were a chemical compound of iron with its carburet, 

 or a mechanical union of carbon and iron. Crystals of carburet of iron 

 were exhibited ; and it was proposed that experiments be tried, with a 

 view to the elucidation of the question. 



6. Donation. — The Annual Report of the Institution of Civil Engineers, 

 for Session 1839. From the Institution. (624.) Thanks voted. 



2Tth March. — Sir J. Grab cam Dalyell, Kt. President, in the 

 chair. The following communications were laid before the 

 Society : — 



1. On the best method of burning gas for the purpose of illumination. 

 By Sir John Robison, K.H. Sec. R.S. Ed.— C.S.A. (.582.) 



The object of this paper was to poiiit out the most economical mode 

 of burning gas for the purpose of giving light ; by peculiar construction 

 of the burners, and the proper size and fitting of the glass chimneys ; and 

 the disuse of obscured shades. It Is found to be more economical, with 

 anj' burner, to burn the gas to the full height it can attain without smoking. 

 If a smaller quantity of light be wanted, it is better to use a smaller burner 

 than to reduce the flame of a larger one. The best efiect of an argand 

 burner is attained when the holes are all of one size, so that the flame 

 shall be of an equal height all round. The paper also described the me- 

 thod of burning gas in street lamps, pointed out by Sir Jolm Robison, and 

 now very generally used in Edinburgh, so as to prevent the moisture from 

 being condensed on the inside of the globes, and rendering the light ob- 

 scure. 



The thanks of the Society were given to Sir John for this communica- 

 tion. 



2. Description of a Substitute for Door Springs. By Mr John Gilchrist, 

 10 Middle Arthur Place. A model was exhibited. (631.) 



This appeared to be an ingenious method of applying lever power, in- 

 stead of springs, for the purpose of shutting, and keeping shut, doors open- 

 ing either way, and by which the greatest power is obtained just where 

 it is wanted, viz. when the door is shut. — Referred to a Committee. 



3. Dr Fyfe, V. P. described Mr Talbot's process of Photogenic Draw- 

 ing. 



