146 Eutton — Physical Geology of Malta. 



It contains a small quantity of carbonate of magnesia, prin- 

 cipally in the lower parts. Its specific gravity is two, and 

 it is capable of absorbing three gallons of water per cubic 

 foot. (Marked 1 in sections.) 

 Heterostegina-bed. A reddish-yellow sand, or sandstone, con- 

 taining in places large quantities of dark-green grains of 

 glauconite (silicate of iron and alumina), which then give 

 their colour to the rock. It varies in thickness from 50 

 feet to 1 foot, and in some places seems entirely absent. 

 Marl. A dark-blue or light-brown laminated Marl, containing 

 nearly 25 per cent, of carbonate of lime. Its thickness 

 varies from 50 to more than 100 feet. 



(The Heterostegina-bed and Marl, are together marked as 

 2 in all the sections.) 

 Freestone. A pale-yellow, or grey, granular, siliceous Lime-stone, 

 traversed by several thin beds of dark-coloured nodules. 

 This Limestone contains carbonate of magnesia and clay in 

 very perceptible quantities ; the former being most abundant 

 in the pale-yellow varieties, the latter in the grey. It is 

 much jointed, ovnng, probably, to the quantity of clay that 

 enters into its composition ; and it contains numerous fossils, 

 including some Diatomacece (Synedra, Navicula, Pleurosigma, 

 and Siirirellaf). Its specific gravity is 2.5, and it can 

 absorb 1^ gallons of water per cubic foot. Its thickness 

 is about 200 or 250 feet. (Marked 3 in sections.) 

 Lower Limestone. A hard Limestone, usually white, but some- 

 times light-brown ; very variable, but generally composed of 

 rolled calcareous debris, the pieces of which vary in size from 

 a few lines to two or three inches. The light-brown parts 

 are often crystalline. It contains, besides other fossils, large 

 quantities of Foraminifera, and a few Diatoms [Navicula). 

 I can find no trace of magnesia in it. Its thickness is more 

 than 400 feet, but how much more it is impossible to say, 

 as no rock is found below it. Its specific gravity is 2.7. 

 (Marked 4 in sections.) 

 Of these strata the Elephant-bed, as at the Krendi fault, and at 

 Fomm-er-rih, rests sometimes unconformably on the Upper Lime- 

 stone (see Section, Plate IX. Fig. 7, and Plate VIII. Pig. 4). 

 The, others are always conformable, and generally pass gradually 

 into each other ; the most distinct division being between the Free- 

 stone (3) and the Marl (2) ; and this is perhaps entirely owing to 

 to the very different colour and composition of the beds. We must not, 

 however, jump to the conclusion that, because these beds appear to 

 pass one into the other, no great period of time elapsed between the 

 formation of one and the other ; for, in one instance, at any rate, we 

 have proofs to the contrary. The Lower Limestone (4) often passes 

 quite insensibly into the Freestone, so that it is impossible to say 

 where one ends and the other begins ; yet the surface of the Lower 

 Limestone is very uneven, and had evidently undergone consider- 

 able denudation before the Freestone was deposited. Large bosses 



