THE MICROSCOPE. 33 



has sometimes been spoken of disparagingly, as if the conclusions 

 to which it led were uncertain, and hardly worth the labor of arriv- 

 ing at them. We occasionally hear taunts levelled at the ' waist- 

 coat-pocket geologists,' who carry home little chips of rock, slice 

 them, look at them with their microscopes, and straightway reveal to 

 their admiring friends the true structure and history of a whole 

 mountain range or region. That the sarcasm is often well deserved 

 must be frankly conceded. Some observers with the microscope 

 have been so captivated with their new toy as to persuade themselves 

 that with its aid they may dispense with the old-fashioned methods 

 of observation in the field. But there could not be a more fatal 

 mistake. The fundamental questions of geological structure must 

 be determined on the ground. The microscope becomes an invalu- 

 able help in widening and correcting the insight so obtained ; but 

 its verdict is sometimes as ambiguous as that of any oracle. In 

 any case it must remain the servant, not the master, i >f the field- 

 geologist." 



M. Renard has undertaken a most elaborate investigation (chem- 

 ically and microscopically) of sections of the rocks brought home by 

 the "Challenger," with the view of determining whether they were 

 to be considered as volcanic or to be classed among the crystalline 

 schists. If they belong to the latter, they must once have lain 

 deeply buried benealKi overlying masses, by the removal of which 

 they have been revealed. They would thus go far to prove the 

 former existence of much higher and more extensive land in that 

 region of the Atlantic ; land, too, not formed of mere volcanic pro- 

 trusions, but built up of solid rock-masses, such as compose the 

 framework of the continents. If, on the other hand, the rock is 

 volcanic, then the islets of St. Paul belong to the same order as the 

 oceanic islands all over the globe. The Abbe inclines on the whole 

 to the side of the crystalline schists, but Professor Geikie considers 

 that the balance of proof is decidedly in favor of the volcanic origin 

 of the rock. — Royal Medical Journal. 



Green Bearded Oysters. — For some time past it has been re- 

 ported that the oysters taken from the Shrewsbury River beds were 

 diseased and afflicted with what is known as "green gill." Mr 

 Eugene Blackford, one of the New York Fish Commissioners, has 



