82 LESSONS IN CHEMISTRY. 



will be traced the boundaries of the large portion of the 

 island which the granite covers, rising on the coast in 

 northern Down into the graceful tops of the Moume moun- 

 tains, and composing the chief mountain ranges in Louth 

 and Armagh; still farther north forming the uncultivated 

 uplands of Donegal ; running again more than sixty miles 

 south-west of Dublin, and on the far west coast of the bay 

 of Galway, opposing a rocky barrier to the Atlantic. In 

 the north, particularly in Antrim, we find several rocks 

 basalt, white-chalk limestone, green sand, &c. of a different 

 kind from those which I have just mentioned, and which 

 give that portion of the island its peculiar character. 

 / 1 1 9- When we examine the composition of the various rocks 

 I which exist in this and in other countries, we find that they 

 I are composed of the same materials which analysis discovers 

 / in the soil. The study of the rocks of the country is there- 

 fore of interest to the farmer, and the character of its soils 

 , may in a general way be predicted from an examination of 

 \ a map on which its prevailing rocks are represented. The 

 'crumbling of a trap rock we may infer will afibrd a rich 

 loam, like what is found in many parts of Antrim, while the 

 granite rocks, especially if much elevated or exposed, will 

  yield a poor and unproductive soil. Frequently, however, 

 . the soil of a district differs exceedingly in composition from 

 the rock upon which it rests, and consists of materials earned 

 I by floods of water or other causes from rocks at a con- 

 \ siderable distance. The rich soils which gave the deltas of 

 Egypt their ancient renown, have been derived from the 

 mud earned down by the waters of the Nile, and the fields 

 (polders) of the Dutch farmers, are formed from the earthy 

 materials washed from the plains and mountains of Germany 

 by the waters of the Rhine, and which the industry of that 

 people, by means of dykes have preserved from the action 

 of the sea. The Rhine, we are told, brings with it 400 

 tons of solid matter daily. In many districts in Ireland, the 

 soil is composed of transported materials consisting of clay 

 and rolled limestone, and some of these deposits are of a 

 remarkably productive character. It would be impossible, 

 without entering into such details as would be out of place in 

 this work, to describe intelligibly all the varieties of rock 

 which occur in Ireland. It will however serve to extend 

 your knowledge of the composition of soils, to give a short 



