862 THE JOURNAL OF GEOLOGY. 



Unfortunately the lateness of the receipt of the paper prevents a more 

 special account of apparatus and methods. The field, however, is full 

 of promise. It would seem that at present a chief desideratum in this 

 kind of work is to so choose the conditions of experimentation in the 

 laboratory that, if not the same, they may be at least comparable to 

 natural conditions as far as possible, that the results may be suggestive 

 less of how the process may take place and more of how in nature it 

 did take place. The work of Professor Reyer has been of undoubted 

 value, and will, we hope, stimulate to further careful investigation in 

 this direction. E. C. Quereau. 



