389 Royal Society, 
be formed so as to cut glass the same as a-diamond, But that 
their durability is shorter m proportion as they are softer. 
May 9. . A letter to the President by Chapman, Esq, 
M.R.1.A. was read, detailing some observations and conjectures 
.on the geological formation of coals. The author had reason te 
suppose that coals were formed from peat; and to illustrate this 
opinion he has observed the depth of peat bogs in Ireland, and 
in the north of England, aud compared the results with the 
coal-mines at Newcastle, wherice he writes. “fhe deepest peat- 
bogs are from 30 to 40 feet; and he finds by calenlation that if 
this mass was compressed, it would be about equal to the strata 
of coal at Newcastle, although it is far from equalling those in 
Staffordshire. He also traced the analogy between the timber 
or trees found in peat-bogs and on the sea-shores of Northum- 
berland, and the gritstone found in the Canton mine at New- 
castle. This stone, specimens of which have been sent to the 
British Museum, has the perfect form and appearance of trees ; 
and even its apparent fibres are such as to leave no doubt of the 
kind of wood which had preceded the present sand or grit. It 
appears that this ligniform stone fell from the roof of the pit, 
and. had been in an erect position, the same as trees are often 
found in peat-bogs in the natural mode of growth. — In falling, 
these stones leave behind them the model of their bark, which 
the author thinks has been converted into canal coal. He also 
took the specific gravity of peat, which he found to be.in general 
1200, and noticed the peculiar oval form into which trees are 
compressed in the earth. The combustion which assisted the 
change of peat into coal, he considers, may have been effected 
by means of the martial pyrites. 
May 16. A letter from Mr. Mornley to Dr, Wollaston was 
tead, describing an immense block of meteoric iron found in 
Brazil, about 50 leagues from Bahia. This extraordinary mass 
was discovered near the bed of a river, in a sterile country, where 
the granite rocks occasionally surmount, and are never more than 
twelve feet below the surface of the soil; there are few trees, and 
those stunted; and hedges are formed of a species of euphorbia, 
the juice of which emits a phosphorescent light, and is highly 
deleterious to the skins of animals. The block of meteoric 
iron measured about 6 feet by 4, and the author calculated that 
it contained 28 cubic feet, and weighed 14,000lbs. An unsue- 
eessful attempt was made about thirty years ago to transport it to 
Bahia, and for this purpose forty pair of oxen were employed ; 
but the apparatus failed, and the attempt was abandoned. It 
was removed only some yards, and now lies in lat. 10° 33’ south. 
There are thermal springs in that country, the temperature of 
which was from 81 to 10], the atmosphere being 77 and i 
. the 
