148 STODDART, ON MICRO-GEOLOGY. 



at a meeting of scientific persons in London only two years 

 since, one of them is reported to have risen to deny its utility. 



It may, perhaps, be asked, what has all this to do with the 

 present subject? — how can a rock or mineralogical specimen 

 be a microscopic object? Can we discern their component 

 parts ? can we distinguish between a sulphate or a carbonate, 

 a nitrate or a chloride? Yes, and much more. Ask pure 

 chemistry what is contained in the slice of a rock. It will 

 analyse it to the Tr-ii'Truth of a grain, and tell to a fraction the 

 amount of carbonate of lime, silica, iron, and trace of organic 

 matter ; but here its information will end. Now ask the 

 microscopist, and he will tell you that it is formed of coatings 

 of carbonate of lime, one over another, till many tons of 

 pin's-head like bodies arise, each imprisoning in its centre an 

 exquisite little rhizopod. 



Almost every stratum, more or less, abounds in objects that 

 cannot be studied by the unaided eye. The Silurian and 

 Carboniferous Corals, the Cretaceous Foraminifera, or Crag 

 Polyzoa, alike attract our attention. It therefore is seen 

 that the microscope is a necessary adjunct to the geological 

 apparatus. By the microscope it was that the so-called 

 Basilosaurus (the supposed king of reptiles) was deposed and 

 placed at the bottom of the mammals. The Saurocephalus 

 "was another so-called reptile, till the microscopic examination 

 of its bones proved it to be a fish. 



We frequently find shells so much alike that it is often 

 difficult to say w liether or not they are the same species ; but 

 a piece of a valve placed under the lens determines the ques- 

 tion, showing one dotted, another striated, spinous, reticu- 

 lated, or covered with innumerable but always constant 

 patterns. The Cambrian, or oldest fossiliferous strata known, 

 were for a long time supposed to be barren of all organic 

 remains, and were thought to be nothing more than mud 

 deposits of the earliest Silurian beds. At length in some of 

 the bottom rocks near Bray Head were found some curious 

 little zoophytes, named, after their discoverer, Oldhamia. This 

 is the oldest animal known, and, so far as yet discovered, was 

 probably the first being created on the face of our globe. 



After the most ancient period had passed aAvay, we find 

 the animal kingdom to progress considei'ably ; and as the Silu- 

 rian system passed over the terrestrial scene, a large mass of 

 limestone was gradually formed, in which are corals, encri- 

 nites, and Polyzoa of the most beautiful structure, frequently 

 requiring a high power to bringout all their delicate mouldings. 



It was the Silurian period that first gave birth to the ento- 

 mostracous and foraminiferous races, curious forms of which 



