490 



H. P. GUSHING — ASYMMETRIC DIFFERENTIATION IN SYENITE 



number 10 had been used in the calculation instead of number 9 the 

 discrepancies would have varied largely, or, in other words, that the dif- 

 ferences between numbers 5 and 6 of this table are of the same order 

 as those between 8 and 9 or 9 and 10 of the original table. It is not 

 thought, therefore, that the calculation can be regarded as furnishing an 

 argument against the general hypothesis, though it is not maintained 

 that it is of any especial value, owing to the assumptions which enter 

 into it. 



In attempting a calculation of the soaked rock (analysis 6 of the 

 original table) the same difficulty is met as in the previous case, namely, 

 lack of an analysis of the anorthosite gabbro near by. Prom study of the 

 thin-section this is estimated to have a composition similar to that of a 

 mixture of the analyzed gabl)ro and anorthosite gabbro in the proportion 

 of 35 per cent of the former and G5 per cent of the latter. Labradorite 

 augen are more abundant and conspicuous than in the previous case, 

 where a half and half mixture was assumed. Obviously there is the same 

 uncertainty here as appeared in thp previous calculation, the somewhat 

 abnormal character of the anorthosite gabbro of the analysis. Since the 

 calculation is precisely similar to the last, the analyses of the gabbro and 

 anorthosite gabbro are not repeated and column 1 of the following table 

 is the combination of 35 per cent and 65 per cent of the two respectively. 

 The adjacent syenite which is supposed to have soaked the other rock 

 is of about the basicity and cliaracter of that of analysis 9 of the original 

 table, appearing here in column 2. These two are combined in the pro- 

 portion of 56 per cent of the former and 44 per cent of the latter, the 

 result appearing in column 3, with the analysis of the soaked rock in 

 column 4 and the discrepancies in column 5. 





1 



2 



3 



4 . 



5 



SiO,, 



50.15 

 21 90 

 9.82 

 2.61 

 9.31 

 3.49 

 1.49 



59.7 

 19,52 

 6.81 

 .78 

 3.36 

 5.31 

 4.14 



54.36 

 20.87 

 8.5 

 1.8 

 6.69 

 4.3 

 2.65 



54.38 

 20.53 

 8.28 

 1,99 

 5.39 

 5.2 

 3.4 





ALOf, 



+ .34 



FejOj 



4- .22 



MgO 



— .19 



CaO 



-f-1.3 



Na.,0 



— .9 



K,0 



— .75 









98.83 



99.62 



99.17 



99.17 





There is more lime and less alkalies in the calculated mixture than in 

 the actual rock, just as was true in the previous calculation. This might 

 suggest either an error common to both, due to the assumed mixture of 



