SCIENTIFIC SUMMARY. 
103 
200,000 tons would only re-lay 200 miles annually. If steel rails were ad- 
mitted free, their consumption in America would he enormous, and the 
advantage to railway companies correspondingly great. 
The Chemical Nature of Cast Iron. — The committee appointed in 1869 
have reported that they have made very little progress. They promise a 
good report for the next year. Those on the committee were Mr. David 
Forbes and Messrs. Abel and Matthiessen. The latter is unfortunately dead 
since. 
South African Diamonds continue to arrive, and some of them are ex- 
tremely fine. The subject was discussed in a paper read by Professor Ten- 
nant before the Society of Arts on November 23. The paper appears with a 
woodcut in the u Journal ” for the 25th, and may be of interest to some 
readers. 
Ozokerit. — The mineral ozokerit, says a recent number of the (i Medical 
Press,” the celebrity of which has been achieved, it is said, by an expendi- 
ture in advertising of something approaching 15,000/. by Messrs. Field, of 
London, was exhibited by Mr. Henry Draper, at the last meeting of the 
Dublin Chemical Club. This substance is found overlying the coal mea- 
sures in Moldavia, Austria, and at the Urpeth Colliery at Newcastle-on- 
Tyne. It is purified by distillation, and afterwards by pressing it and 
treating it with sulphuric acid ; when purified it has an extremely high 
melting point. For this characteristic, which has not been found in any 
other similar substances except wax, it is selected for the manufacture of 
candles, because it affords a larger wick and a better illuminating power at 
a lower price. From Mr. Draper’s experiments it appears that pure ozokerit 
and white wax melt at 150° F., the candle as sold at 138°, paraffin at 129°. 
There is, therefore, an admixture with it of some other material. Even the 
residue of ozokerit, after its purification, has been utilised. The late Dr. 
Matthiessen, whose untimely death by his own hand is still in our memory, 
patented it as an insulator for telegraphic wires, for which purpose it is 
said to be eminently suitable. 
Enamelling of Iron. — This important subject is discussed by Herr Dr. E. 
M. Dingier, in the Oct. (No. 2) number of u Dingler’s Journal,” and the 
paper is well reported in the u Chemical News.” The . author first points 
out that the main difficulty in the process of enamelling iron consists in the 
fact that the expansion of the metal by any increase of temperature is far 
greater than the expansion of glassy bodies, and that, as a consequence, the 
enamel is very liable to come off by a sudden increase of the temperature of 
the enamelled metal. This defect, says the author, is best mended by the 
use and application of a * ground or first layer, which does not become 
quite fluid by heat, but retains a pasty consistency and porosity, which 
enable it to give way to some extent by the expansion. On this first layer, 
the second or covering layer is applied. The author recommends the fol- 
lowing mixture as ground or first layer : — Pulverised quartz, 30 parts ; 
borax, 16£ ; white-lead, 3 parts. These ingredients are fused together, and 
the molten mass is pulverised and intimately mixed with 9 parts of very 
finely ground-up quartz, 8§ parts of washed pipeclay, and | part of mag- 
nesia alba. The second, or covering layer, is prepared by melting together 
a mixture of 37^ parts of pulverised quartz, 27 h of borax, 30 of oxide of tin, 
