612 



Mr. J. Beete Jukes and the Rev. Samuel Haughton on the 



the consideration that the sum of the silica, alumina, &c., is equal to the total 

 difference in weight of the new granite and the old. 



A number of hypotheses may be made, which would enable us to solve the 

 equations (22). The following are only given as an example of the method of 

 procedure : — 



Hypothesis A. — Let the impurities added to the molten granite equal in weight 

 the mass to which they are added. 



Adopting^this hypothesis, which is certainly not a probable one, and taking 

 Jf equal 100 tons, C becomes 200 tons, and the following values may be found 

 for the elements added : — 



Table XIII. 



Impurities added to 100 tons of Main Chain Granite, to make up 200 tons of CooUattin Granite. 



Hypothesis B. — Let the impurities added consist of clay slate and other 

 matters, the ratio of the silica to the alumina being 90 : 52. 



This proportion of silica to alumina is the proportion of two atoms of silica 

 to one of alumina, and is one that is often met with in clay slates. 



From it we obtain from the first two of equations (22), the following 



value ; — 



C= 139-2. 



Substituting this value in the equations, and making M equal 100, we 



find, 



