32 R. THRELFALL. 
work of this kind, and M. Lippmann appears to have had a 
fair share of it, and has actually photographed simple objects—_ 
such as a pot of geraniums, the photographs (negatives in the 
ordinary sense) exhibiting the colours of the original. So far as 
IT know, he has not succeeded in printing in colours. The 
suggestion of the method appears to have been due to Zinker in 
1868, and so is of considerable antiquity. I see no reason why 
we should not have coloured photographs of some kind within 4 
reasonable period. 
The next point on which I will touch refers to the use of 
the electric furnace, for within the last few years a magnificent 4 
series of researches has been carried out with its aid by 
Moissan on hitherto infusible substances. The simplest form of 1 
electric furnace merely consists of a lime block hollowed out and — 
provided with a lid. Two carbon poles meet in the centre of the 
cavity, and are the seat of an arc light whose power is only 
limited by the engine power available. The end result is that 
a considerable fraction of the energy of the boiler fire is eon 
centrated in the space of a few cubic inches, and the temperature 
attained is correspondingly high. By this furnace Mr. Moissa 
has not only been able to produce small diamonds, but he has — 
been able to prepare considerable quantities of the metals of the — 
chromium group, (and lately with an improved furnace of titanium); — 
which, it is not too much to say, were unknown hitherto in any 4 
thing approaching an ingot form. The latest development appears | 
to be the manufacture of calcium carbide from lime and coal dust. 
This process we owe to Mr. Willson, an American, and it appears 
likely to have some influence in the arts; for the massive 
calcium carbide, when acted on by water, yields acetylene in @ 
very pure state, and this either asa means of enriching gas, or a5 le 
starting point for organic synthesis is a very valuable substance 
Some years ago Mendelejeff advanced a theory of the production 
of petroleum from its elements under the influence of high te” 
peratures, so that Mr. Willson’s discovery will come as cheering 
