372 
Scientific Intelligence.— Arts. 
tion : dry sulphate of soda, 100 parts; slaked lime, 12 ; powder- 
ed charcoal, 19 ; sand, 225 ; broken glass, from 50 to 200. 
These proportions give a rich coloured glass, which may be em- 
ployed with advantage in glass-houses, where a fine quality is 
sought after. The following is the second way of operating with 
sulphate of soda ; the proportions may be as follows : dry sul- 
phate of soda, 100 parts ; slaked lime, 266 ; sand, 500 ; broken 
glass, from 50 to 200. According to this process, it is obviously 
easy to operate in a regular manner, and to avoid expensive 
trials in the manufacture. — Annales de V Industrie Nationale. 
27. On the advantages of' improving the qualities of Cutting 
Instruments , hy Burnishing , and thereby condensing their edges. 
By Thomas Gill, Esq.— -The condensing process of hammer- 
hardening the edges of cutting-instruments, such as the graver 
and the scythe, has naturally led us to consider the action of the 
burnisher upon the edges of other cutting-instruments in a simi- 
lar light ; and to infer that a great part of the benefit derived 
therefrom must be owing to its condensing effect , as well, also, 
to its giving the edges a more favourable position for effecting 
the different purposes they are applied to. The currier's shav- 
ing hnffe is the first instance we shall quote, where, after renew- 
ing its edge, by whetting it upon the proper whet-stone, as well 
as continually during its use, the edge is always burnished. 
The next, and a familiar example, is in the steel-scraper used 
by the cabinet-makers to smoothen the surface of hard wood 
after the toothed plane, previous to varnishing or polishing 
it. When the edge of this hardened and tempered flat piece of 
sheet-steel becomes dull, it is renovated by placing it upright, 
and whetting it upon the oil-stone ; it is then whetted upon each 
side, to remove the burs ; and, lastly, burnished upon the face 
of it, towards each side, so as to throw the edges outwards. It 
is held in a sloping direction in use, exactly as a piece of bro- 
ken window- glass is held when used as a shave, for which, how- 
ever, it is an admirable substitute, as it performs its work in a 
similar, though much more perfect, manner. The next example 
is furnished from the practice of a late ingenious mathematical 
instrument-maker, Mr R. Fidler, who was continually employ- 
ed by the late Mr W. Lowry, the celebrated engraver, when he 
had any instruments to be made, for his business of mechanical 
