16 



many parts of Gozo. It varies in thickness from 20 to 50 

 metres or more and is made up of a number of distinct 

 layers with intervening beds of shells and coprolites, 

 which are particularly rich in phosphates. This rock is 

 made up of minute calcareous shells of Foraminifera, 

 cemented together by carbonate of lime, and is naturally 

 rather soft, porous and moist, but is almost everywhere 

 glazed over by a thin seinicrystalline crust, which is prac- 

 tically impermeable to water, formed in the course of time 

 by the carbonate of lime dissolved by rain water and 

 deposited again on evaporation. The upper layers of this 

 formation contain pockets of red soil of good quality, 

 suitable for most fruit trees. By 'levelling the irregular- 

 ities and breaking up the thin hard crust which encases 

 the rock, the natural moisture contained in the rock 

 becomes available for the trees and therefore this opera- 

 tion is generally performed whenever it is intended to 

 transform a field into an orange grove or an orchard. 



The lowermost formation consists of the Lower 

 Coralline which may be called the basement or pedestal 

 of the Maltese Islands, but is only exposed over limited 

 areas. This rock, like the preceding, and still more like 

 the Upper Coralline, consists chiefly or almost entirely 

 of carbonate of lime and is rich in fossils and therefore in 

 phosphates. It is usually very hard, with a semicristalline 

 or crystalline texture, and is often altogether imperme- 

 able to water. It is particularly rich in pockets of deep 

 red soil of excellent quality, often at considerable distance 

 from the surface. This soil is always of a deep red 

 colour, and is the best of the three types of red soil above 

 mentioned. Trees growing on this formation have the 

 advantage of the superior quality of the soil, but the rock 

 is too dry, and in a prolonged drought the trees are apt 

 to suffer severely unless watered. Where the soil is deep 

 enough, and permits the growth of trees which ordinarily 

 are not watered, such as figs, grapes and stone-fruits, the 

 fruit may remain somewhat undersized, but the loss in 



