PoLttoK—On the Iieselguhr of County Antrim. 35 
grams, and its actual volume was 68 cubic centimetres, correspond- 
ing to a density of 8069. If we may take the volume of the 
water absorbed as a measure of the porosity, we see that every 
100 c.c. of Kieselguhr has pores of a total capacity of 55:9 e.c. for 
absorption of liquids of any kind. It is interesting to note that 
this would give an absolute density of the solid skeleton of the 
IGeselguhr of 1-829, the density of solid quartz being 2°6, but we 
have no right to suppose that the pores when treated as above are 
fully saturated. 
In July of 1898 I visited Toome Bridge, and found that the 
deposit was being worked on the east bank by Messrs. J. and F. 
Grant, who gave me every opportunity of examining the character 
of the deposit, and to whom I am indebted for the following 
analysis of the deposit at this point. 
ANALYsIs OF KiksELGUHR FRoM T'oomE Bripee, County 
ANTRIM. 
Sample from the Middle of the Deposit. 
As Received. Calcined. 
Silica (soluble),. : : ‘ 5 57°12 per cent. 66°50 per cent. 
Silica (insoluble), ; : : : NG) g IBID 55 
Alumina, : : : : : So) be OH op 
Oxide of Iron, . d : : : BAN) 6, 24s 
Lime, AEE Re Se CEE NA 1B. 
Magnesia, : : ‘ : : OSS og 0-96 Ge 
Alkalies, ; 5 : : F 052. Siuaes O38 55 
Organic Matter and Combined Water, eae 7 5 — is 
Moisture, ; : : : 5 Gos) a. — Bs 
100:00,, HOOWO gp 
At Toome Bridge the deposit is some four feet thick ; and, after 
cutting and drying in the sun, the Kieselguhr is of a very white 
colour, with a few roots through it, but otherwise exceedingly pure 
and, after drying, of surprising lightness. 
The deposit, as it rests on the top of peat, and is covered only 
by vegetation, is obviously of exceedingly recent formation. It 
extends all along both banks of the lower Bann, from Toome 
Bridge, where the river emerges from Loch Neagh, right down 
to Coleraine. At Toome Bridge the deposit, so far as one can 
judge by superficial indications, and without actually proving 
D2 
