NOTES ANT) QUKTITES. 
151 
similarly in the Isle of Lemnos, and at Magnesia, in Asia Minor. It is 
there associated with magnetic iron or crystallized magnetite. It occurs 
along with diaspore in the dolomite of St. Gothard. It occurs near 
Ephesus, and also in the Isle of Naxos, in the same way. Here are five 
specimens of corundum in its opaque, common form. In its finely-divided 
state it is commonly known as emery, which is nothing more than the com- 
mon form of the true sapphire. Some of the analyses of this substance 
give water as an essential constituent, but the sapphire and the ruby are 
nothing more than crystallized alumina without water. But there are 
analyses of some two or three specimens of corundum in which we find 
water given as a constituent. An analysis of corundum from Asia Minor 
gives 3-7 per cent, of water, and an analysis of corundum from India 
gives 31 per cent, of water. In these cases, probably, they contained 
diaspore associated with them. There is a difficulty in many of these 
analyses, and we cannot extract rational formulae of the results obtained 
by approximate analysis, because these crystals have the power of enclosing 
within their mass a very large amount of matter which in no way enters 
into the chemical composition of the mineral itself. It is there as so mucli 
foreign matter entangled in the crystal, and yet the crystal shall have a 
definite form, and so forth. There is a portion of matter which we must 
not take cognizance of, but we have no means of separating it mechani- 
cally from the mass. It all comes into our results, as we have no way of 
separating this dirt, as metallurgists call it. 
Now for some examples of the so-called aluminates. There is a form of 
ruby which is an aluminate of magnesia. It is coloured a fine rich 
colour, apparently with chromate of potash ; but of course it is not equal 
to the oriental ruby. It consists of one equivalent of magnesia and one 
of alumina. Its formula is, MgOAlgOg, so that you see that the alumina 
contains three times as much oxygen as the magnesia. It may be obtained 
beautifully crj'-stallized, and was so obtained by Ebelmen. It is made 
simply by heating magnesia and alumina with fused boracic acid, with 
the addition of a little chromate of potash. The experiment was made 
in exactly the same way as that with reference to the crystallized alumina 
prepared in the porcelain furnace at Sevres, near Paris, already spoken 
of. Ebelmen obtained in this way distinct crystals of aluminate of mag- 
nesia, having a fine ruby-red colour. Tliey are exceedingly small, but 
they are, nevertheless, instructive, small though they be. Then, by 
adding a little cobalt, he obtained crystals of the same form, having the 
characteristic and beautiful blue colour of the natu^-al mineral. 
NOTES AND QUERIES. 
Typical Mammalia in British Museum. — Dear Sir, — Allow me to 
point out to you an omission in your list of figured specimens of fossil 
mammalia in the British Museum ('Geologist,' March, 1864). I have 
lately described and figured, under the name of Hyana antiqua (Annals 
and Mag. of Nat. History, January), a molar tooth from the Hed Crag of 
Suffolk, which is now in the national collection. As this announcement 
may stimulate others to search in the same direction, I trust you will in- 
sert it in your journal.— Truly yours, E. Ray Lankestee. 
8, Savile Eoto\ W. 
