Frazer.] 



404 



[April 16, 



TRA.CHyTIC. 



PER CENT. OXYGEN. OXYGEN KATIO. 



Silicon 36.80 39.87 89 87 



Aluminum (say 7 p. c. Al.Os). . 3.71 3.28 ) 



Iron (say 7.23 Fe A) 5-06 2.17) ^'^^ 



Calcium.... 1.03 0.41] 



Magnesium 0.17 0.11 i 



Sodium 2.37 0.83 j ^'^^ 



Potassium 3.47 0.71 j 



Oxygen 47.38 



Total acid and basic rad- 

 icals 52.61 



In the Journal of Science and Arts, Vol. IX, March, 1875, is a paper 

 by Mr. Geo. W. Hawes, on the Trap Rocks of the Connecticut Valley, in 

 which a number of closely accordant analyses of dolerites are given, the 

 specimens being selected from various localities in the Mesozoic Sand- 

 stone Belt of that State. 



A Dolerite taken from a dyke knovrn as West Rock, and standing west 

 of New Haven, gave to Mr. Hawes the following results, which have been 

 embodied in the form of the preceding hypothetical compositions. 



ANALYSIS I, OF WEST ROCK. 



PER CENT. OXYGEN. OXYGEN RATIO. 



Silicon 24.86 26.94 1 



■ Phosphorus 0.06 0.08) '^^'^'^ 



Aluminum 7.55 6.65) 



Iron (from FeA) 3.48 1.07) 



Iron (from FeO) 6.36 1.90] 



Manganese (from MnO) 0.32 0.10 



Calcium 7.58 3.00 ! ggg 



Magnesium 4.67 2.96 i 



Sodium 1.59 0.56 1 



Potassium 0.32 0.06^ 



Ignition 0.63 



Oxygen 43.32 



Acid and basic radicals.. 56.42 



On comparing this analysis with the hypothetical composition of 

 Cotta's Basic Igneous Rock, it will be observed that the Silicon (inclu- 

 ding under this head the small per cent, of P. present in West Rock), is 

 almost the same in both, as also is the percentage of radicals in the pro 

 toxide bases, while the per cent, of Oxygen of both protoxide and ses- 



