574 
POPULAR SCIENCE REVIEW. 
holding a cubic foot, the candle burnt 6 minutes. In a coal mine, where 
the air is vitiated, it would not burn so long ; and Mr. Keene proposes to 
prohibit working in places where the candle will burn not more than three 
minutes. 
Safety of the Davy Lamp . — At a late meeting of the North of England 
Mine Engineers, the President, N. Wood, Esq., stated that at a particular 
colliery, the workmen always made the gauze of their lamps red hot before 
using them, in order to expel the oil contained in the wire. Rough experi- 
ments had been made, and it was found that new gauze was sometimes 
capable of passing the flame of gas in consequence of the oil it contained, 
and which is used in the manufacture of the wire. This may account for 
explosions which have taken place under mysterious circumstances, and 
when the lamps have appeared in good condition. Whenever a lamp shows 
any indication of explosive gas, it should be instantly withdrawn ; if this 
precaution is attended to, the Davy may still be considered a safe lamp. 
Further experiments are to be made. 
PHOTOGRAPHY. 
T HE principal novelty in the way of photographic materials which we 
are called upon to notice, is the so-called “ enamel paper,” intended 
to be used in printing as a substitute for that prepared with albumen. The 
new article appears to have been originally manufactured in Germany, 
but already there are several kinds known in commerce ; — all of them are, 
however distinguished for their fineness of texture and the extreme lustre 
of their surfaces — peculiarities attributable to the employment of mineral 
pigments, conjointly with albumen, in their preparation. With regard to 
their exact nature many statements have been made, and the white pigment 
has been shown to consist sometimes of sulphate of baryta, and in other 
samples of oxide of zinc, with albumen in all cases as the adhesive mate- 
rial, and a soluble chloride to furnish the necessary elements for the 
production of the photographic image. The paper is rather thick, and 
requires to be manipulated in the same manner as the common albumenized 
material, with the additional precautions of allowing a somewhat longer 
interval for the final washing of the prints, and taking care not to crease 
or fold the enamelled surface, which is somewhat sensitive to incautious 
handling. Varieties of this enamelled paper may be procured in several 
tints of colour ; among others, pale lilac or rose-pink, serving in the repre- 
sentation of subjects where a degree of warmth of tone is appropriate. This 
description of paper appears generally suitable for cartes de visite, stereo- 
scopic pictures, and others of diminutive size ; but the excessive brilliancy 
of the enamelled surface is, for larger subjects, eminently distasteful. 
A suggestion relative to the employment of ammonia for the purpose of 
“fuming” the sensitized surface of papers used in the printing processes 
has not yet been entirely disposed of ; some authorities adhering to the 
opinion that such treatment confers great advantages on the score of 
rapidity of action, as well as in the toning process and subsequent mani- 
