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POPULAR SCIENCE REVIEW. 
Tempering Steel for Tools. — The 11 Chemical News,” quoting from the 
u Bulletin de la Soc. Chim. de Paris ” (Vol. xx. No. 10), says that the fol- 
lowing procedure, due to M. Kulicke, is in use at the works at Saarbruck. 
It serves to restore the nature of steel altered or burnt, and consists in 
plunging the article — previously brought to a cherry-red heat and forged for 
an instant — into the following mixture, and then into cold water : — Tartaric 
acid, 12 parts ; fish-oil, 60 parts ; powdered charcoal, 4 parts ; bone-black, 
16 parts ; yellow prussiate, 20 parts ; tallow, 20 parts ; burnt stag’s hom, 6 
parts. 
Experiments on the Colours of the Diamond. — At the meeting of naturalists 
which took place recently at Wiesbaden, and of which an account is given 
in the “ Chemical News” (February 26, 1874), and in the Mineralogical 
Section, Herr Flight described his experiments on the colours of the diamond. 
A rose-coloured diamond of twenty-nine carats, exhibited at Paris in 1867 
by Coster, of Amsterdam, was bleached in four minutes on exposure to dif- 
fused light, but resumed its colour when heated in asbestos, and retained it 
if preserved from daylight. Two dull yellow diamonds from the Vaal river 
were selected, one of which was preserved for comparison, while the other 
was subjected to modifying experiments. On being heated to redness in a 
current of hydrogen, it was found colourless when cold, but gradually as- 
sumed its colour on exposure to daylight. If heated in a current of chlorine 
the result was the same. 
Crystallographic and Chemical Features of Caledonite and Lanarkite. — A 
paper was contributed to the Chemical Society in December by N. S. 
Maskelyne and W. Flight on the crystallographic and chemical characters 
of caledonite and lanarkite. Some specimens from Leadhills, recently- 
procured for the British Museum, having been found on analysis to have a 
composition differing from that of caledonite, a specimen of true caledonite 
was also examined, and, while neither analysis accorded with that of Brooke, 
both agreed in showing this mineral to be lead sulphate in combination with 
lead hydrate and copper hydrate. Lanarkite was found to contain no water, 
and to be a compound of lead sulphate and lead oxide, as Pisani has shown. 
A Year's Amount of Sulphur. — It seems that in 1871 the Italian (Sicilian) 
mines of sulphur produced .... 6,860,000 cwt. 
The rest of the world in the same year produced . 152,500 „ 
7,012,500 
Equal in gross tons to .... 351,625 
The quantity of sulphur produced from the roasting of pyrites is insignificant, 
this industry being occupied almost exclusively in the production of 
sulphuric acid. 
MICROSCOPY. 
The Structure of Filaria Immitis. — This is very fully described in a 
valuable paper published in the “ Monthly Microscopical Journal,” No. 
LVIII., by Mr. F. H. Welch, F.R.C.S. He says that by the aid of glycerine 
and high microscopic powers the following details were brought out : — The 
