442 
POPULAR SCIENCE REVIEW. 
phane, Estramadiu’a phospliorite, and tlie green fluor spar. He has analysed 
the light emitted : the first is a simple green ; the second is a yellow tinted 
light; composed of gi^een, yellow, and red ; and the third gives two black 
rays, the one in the green, and the other near the orange. 
The Composition of Pyrites Residue. — Dr. Phipson has communicated to the 
Chemical Keios (July 17) the result of his analysis of the residue of pyrites 
obtained in the Drumburgh Chemical Works, Cumberland, where Nor- 
wegian pyrites is principally burnt : — 
Oxide of zinc 
5-50 
,, copper . 
2*86 
,, manganese 
1-60 
„ nickel and cobalt . 
0-12 
,, cadmium 
0-01 
„ lead 
1-67 
„ antimony 
0-04 
Protoxide of iron 
1-17 
Alumina .... 
3-25 
Arsenic .... 
none 
Sulphirr .... 
2-60 
Thallium and indium . 
trace 
Rock . . . . 
15-00 
Peroxide of iron (bv difference) direct 67-00 
65-99 
Lime 
0-11 
Magnesia .... 
0-08 
100-00 
The Iron Works of the ‘ Weald.' — At the meeting of the British Associa- 
tion, W. Boyd Dawkins, M.A., F.R.S., read a paper ^On the Iron Works of 
the Weald,’ in which he expressed the opinion that the works were carried 
on by the Romans. Few persons, he thought, could pass through the 
sparsely populated country between Tunbridge and Hastings without ob- 
serving that they were in the midst of what not very long ago was the 
principal iron district of England. He believed that there was evidence 
worthy of notice that mining was carried on in the Weald some nineteen 
hundred years ago. An opinion was expressed, in the course of the discus- 
sion, that the works were of even stiU greater antiquity, and could be traced 
back to the early British times. 
The Volatile Matter of Coal. — In a paper in the Ameidcan Journal of 
Mining, Professor G-. Hinrichs, in reporting his investigation made to deter- 
mine the volatile matter of vai’ious specimens of coals, thus sums up his 
remarks. The total volatile matter of coal is determined with accuracy 
(1 mgr. on 1 gr. coal), by taking 1 to 2 grammes of undried, pulverised 
coal, heating it for three and a half minutes over a Bunsen burner (bright 
red heat), and then immediately, without cooling, for the same length of 
time, over a blast gas-lamp (white heat). 
The Preparation of Thallium. — At the white vitriol works of the Lower 
Hartz there is obtained by lixiviating the roasted ore in water a liquor 
which is rich in thallium. This rare metal may, according to Bunsen, be 
extracted from this liquor by precipitating, by means of metallic zinc im- 
