324 
POPULAR SCIENCE REVIEW. 
News,” May 19, that this material is known in commerce as the onyx of 
Tecali. It varies in colour from milk-white, yellowish white to pale green, 
certain samples displaying brown veins shading into red. It takes a fine 
polish. Its specific gravity is 2*77. It is readily and entirely soluble in 
nitric acid. Its composition is — 
Carbonic acid .... 43*52 
Lime ..... 50*10 
Magnesia . . . .1*40 
Ferrous oxide .... 4*10 
Manganous oxide . . . 0*22 
Water ..... 0*60 
Silica ..... traces 
99*94 
Sulphur in Coal Gas. — M. A. Virigo states that (“ Chemical News,” 
May 12) he found, in portions of 100 cubic feet of gas made at Odessa, 
respectively 2, 1*81, 1*9, 2*01, and 2*2 grms. of sulphur. He readily detected 
the presence of sulphurous acid in the air of rooms lighted with this gas, and 
demonstrates its ready conversion into sulphuric acid in contact with moist 
organic matter, such as cotton yarn. 
Experiments as to Insecticides on the Phylloxera. — M. Dumas’ book on 
this subject has been published, and has been reviewed in the “Chemical 
News ” of May 2, from which we take the following remarks : — “ As re- 
gards the phylloxera of the roots it is found that the sulpho-carbonate of 
potassium, of which more than 20,000 kilos, have been already used, is a 
rapid insecticide, the only one which certainly destroys the phylloxeras fixed 
upon the roots, and which affords at the same time an efficient nourishment 
to the vine. The sulpho-carbonate of sodium offers similar advantages as 
an insecticide only. The sulpho-carbonate of barium being an anhydrous 
salt, and sparingly soluble, is recommended by its resistance to the action of 
oxygen and to that of carbonic acid, which renders it a poison less rapid, but 
of an effect more durable. As to the winter-eggs the heavy oil of gas-tar, 
and especially the so-called oil of anthracen, seems to be the most suitable 
agent for anointing the branches and for destroying the winter-eggs. The 
application of gas-tar to the branches and of sulpho-carbonates to the roots 
is best performed in the months of February and March. 
Death of Dr. Letheby. — The “ Analyst ” says : “ We have to announce, 
with deep regret — a regret which will be shared by our readers — the death, 
somewhat suddenly, of Dr. Letheby. He had been unwell for some weeks, 
his complaint being, we believe, inflammation of the lungs. Dr. Letheby 
was too well known in the chemical world to require any lengthened 
obituary notice at our hands. We may, however, mention that he was an 
early member of the Chemical Society; that he took his M.B. degree in 
1843, became Ph.D. and M. A. in 1858 ; that amongst the numerous 
appointments which he had held were those of Medical Officer of Health 
and Public Analyst for the City of London ; and that he was the author of 
numerous scientific and hygienic works. He died in his sixtieth year.” 
The Production of Bromine in America. — The “American Journal of 
