216 
POPULAR SCIENCE REVIEW. 
Ensuring the Purity of Silver. — It is no easy matter to make sure of the 
purity of silver. To those, therefore, who are working at this branch of 
metallurgy we commend the admirable memoir of M. Stas, in the Annales 
de Chimie, vol. lvi. p. 413. It has been translated into the Chemical News 
for February 22. 
Composition of Boronatrocalcite. — This peculiar mineral has had its com- 
position variously set down by different mineralogists. Lately, however, 
Mr. George Lunge has taken up this mineral for investigation. In a paper 
published in the Chemical News he goes fully into the history of the 
analyses given by his predecessors, and after explaining the method adopted 
in his own inquiries, he sets down the formula as follows : — 
2(NaO,2B0 3 (+5(CaO,2BO 3 )+42 aqu. 
This is very nearly exact ; there must, however, be a magnesium substi- 
tuted for a very small quantity of calcium. 
The Metal Manufacture of Prussia. — The forges and foundries in Prussia 
amounted in 1884 to 1,421. The total production amounted to 1,610,000 
tons of common metals and 56,701 lbs. of silver, representing in money a 
sum of £5,816,187. 
Telegraphic Communication in Mines. — At the Trafalgar Colliery, in the 
Forest of Dean, Mr. Brain has exerted himself to provide electric communi- 
cation between the men descending the shaft and those in the engine- 
room, and above and below. The instrument is the same as one used on 
the Metropolitan Railway. It is fixed in the engine-room in front of the 
engineer. At the pit bottom the “ hanger-on ” is provided with a pair of 
electrical tappers, coloured respectively white and red. On touching the 
white tapper the bell in the engine-house is instantly struck, and the words 
go on” show themselves on the dial plate attached. On touching the red 
the bell is struck as before, and the word a stop,” in white letters on a red 
ground (as indicative of danger), is shown. By a repetition of the touch 
any number of knocks may be given. This also has been found to answer 
admirably. Electrical communication has also been laid in by Mr. Frost 
from Mr. Brain’s office to different parts of the works, so that he can be 
instantaneously communicated with on any matter affecting the colliery. 
The instruments employed are the common needle, and with bells attached. 
— Vide Mining Journal , February 23. 
Petroleum as Steam Fuel. — Mr. Richardson’s experiments, conducted 
under the auspices of the Lords of the Admiralty, appear to have met with 
more success than some people anticipated. The trials were made with the 
petroleum boiler in Woolwich Dockyard. Mr. Richardson succeeded, 
during the latter period of the experiments, in evaporating 18-91 lbs. of 
water per pound of creosote during a trial of seven hours. The new fuel 
gave off at times a great deal of smoke, which caused a most offensive 
effluvium, the construction of the boiler being such as to impede a full 
gaseous blast, sufficient to destroy and consume the smoke as intended. Mr. 
Richardson has, it is understood, in consequence, applied to the Admiralty 
for a large common marine boiler, for the purpose of future trials. It was 
stated, as the opinion of the local naval engineers and other officers who 
were present, that with such fuel the gunboats in the tropical seas would 
