690 MESSRS MORRISON AND MARSDEN ON THE PREPARATION AND 
whole is then introduced into a gas furnace and heated to the temperature of 
boiling silver, and this temperature was kept up for five hours. During this 
time the silver melts and becomes quite saturated with the boron, which crys- 
tallises out on cooling. Special precautions were taken to allow of very gradual 
cooling, and by means of another furnace, heated to a bright red heat and which 
fitted exactly round the gas furnace, we found it possible to prolong the 
process of cooling over some six or seven hours, thus giving every facility for 
the formation of crystals. 
On opening the plumbago crucible after the operation, care was taken not 
to break the porcelain crucible inside, which was then itself broken open. We 
were particularly careful not to get any of the crucible mixed up with the 
contents inside. These contents were found to be: Ist, a lump of metallic 
silver ; and 2d, a slatish-grey powder. 
The silver was well cleaned and dissolved in moderately strong nitric acid, 
and yielded from its interior a quantity of a steel-grey crystalline powder. 
This powder was then examined in order to ascertain its composition and pro- 
perties. 1st, From its mode of preparation the only substances which could be 
present are boron and silver, and though improbable, owing to precautions 
taken, silica and alumina from the crucible. 2d, A portion was oxidised by 
means of fused nitre, and the mass dissolved in acid and tested for silver, but 
not even a trace was found. Ina similar manner we have also proved silica 
and alumina to be absent ; nor were we able to detect anything except boron. 
These crystals, therefore, must be pure boron, partly graphitic and partly ada- 
mantine. Thus boron is found to have three forms, viz.: amorphous, graphi- 
toid, and adamantine ; although the so-called graphitic boron of WO6HLER and 
DEVILLE has been found to be a boride of aluminium, and the adamantine to 
contain carbon and aluminium. The properties of this powder are as fol- 
lows :— 
1st, It is infusible at a white heat. 
2d, It is not oxidised by air at a white heat, even superficially. 
3d, It is completely oxidised, though slowly, by fused nitrate of potash. 
4th, It is completely oxidised by nitric acid when treated with it for twenty- _ 
four hours at a temperature of 90°-100° C. 
5th, It is completely volatilised when heated with a mixture of hydrofiuess 
and strong sulphuric acids. 
6th, It does not alloy with platinum at a white heat. 
7th, As a powder it is a non-conductor of electricity. 
We have not yet had the opportunity of taking its specific heat. 
We have also tried a number of experiments, not only with silver, but also | 

