426 
Progress in Science . 
r J ul y> 
to observe the image on the screen while in a convenient position for adjusting 
the microscope and illuminators, and also to watch the process during exposure 
and alter the light if needed. The eye-pieces are not to be used, as they con- 
trail the field and blur the image : magnifying power is better obtained by 
distance. A sufficiently strong eye-piece should be used in the telescope to 
give a clear view of the minutiae of the specimen. The hands are the best 
heliostat, as the mirror is within easy reach the whole time. Instantaneous 
micro-photography should be attempted with no power higher than £ an inch, 
and the large condenser only should be used. The alum cell should be re- 
moved during the time of exposure. A special shutter will also be required 
between the large condenser and the objeCt to be photographed : this shutter 
should have no connection with the table, as it would communicate a vibration 
to the whole of the apparatus at a time when everything should be perfectly 
still, except the movements of the animalcule to be photographed. A good 
shutter is made with two boards, having round holes cut in them, and made to 
slide one over the other, an india-rubber band being the motive power. In 
this way one hole may be made to pass the other with such speed that the 
exposure is absolutely instantaneous, and the portraiture of rapidly moving 
subjects rendered perfectly easy with a good light. Some of the results may 
be seen in the Indian Museum, London. The higher objectives, such as the 
i-i6th, work better on the immersion principle, and glycerine or oil of cassia 
may be used instead of water. When substances with a higher refractive 
index than water are used, the focal distance between the objective and the 
glass cover will be increased, and the screw-collar must be adjusted to suit 
the more refractive medium in which the objective has been immersed. When 
oil of cassia is employed, the screw-collar should be used so as to close the 
combination completely, and it will then be found quite possible to focus 
through rather thick covering glass. 
MINING. 
There are 11,294 Chinese miners in the Colony of Victoria, many of whom 
know nothing of the English language; in some of the districts they are em- 
ployed in quartz mines and alluvial mines of great depth and extent, and it 
has been found necessary to inform them of the provisions of the Regulation 
of Mines Statute. The ACt to provide for the Regulation and Inspection of 
Mines has therefore been translated into Chinese. 
A controversy having arisen in Australia on the priority of discovery of the 
nickel deposits of New Caledonia, the Rev. W. B. Clarke, geologist to the 
Colony of New South Wales, recently gave a history of the discovery before 
the Royal Society of Sydney. He showed plainly that the nickel was first 
discovered by M. Jules Gamier in his exploring expedition undertaken under 
the auspices of the French Colonial Office. Mr. Clarke has had in his collec- 
tion, since 1864, specimens of nickel ore sent him by M. Gamier, who, on his 
return to France, made known the abundant existence of nickel in the island. 
Mr. Clarke transmitted an account of the discovery to the celebrated mineral- 
ogist Dana, who described this ore of nickel as a new mineral species, in the 
most recent edition of his well-known work. Prof. Liversidge, of the Univer- 
sity of Sydney, also described the new substance in a learned memoir. 
Clarke, Dana, and Liversidge gave the name of Garnierite to this new ore, in 
honour of its discoverer. The great rise in the price of nickel has latterly 
drawn the attention of manufacturers to these deposits. The serpentines, and 
generally speaking all the rocks which accompany them, are often covered 
with a fine green coating — a silicate of alumina, nickel, and magnesia. The 
price of the metal is now 40 francs per kilo., and the demand is still in- 
creasing. Hitherto it has been extracted from speiss, in which it occurs com- 
bined with sulphur, arsenic, antimony, cobalt, &c. With the ore of New 
Caledonia the extraction of the metal will be simpler and the product less 
impure, the nickel being here combined merely with earthy matters. Though 
of a characteristic green, this new ore may nevertheless be confounded with 
carbonate of copper ; and perhaps the miner, deceived by this resemblance, 
