On Carboniferous Diatomacece. 415 



it contains, and have determined their genera and species ; while, 

 by cutting very thin slices of the coal itself, they have been enabled 

 to study, with the aid of the microscope, its texture and minutest 

 ingredients. 



These researches did not, however, reveal the presence of some tiny 

 little Diatoms which chanced to be there ; thus it has been affirmed 

 that Diatoms were not contemporaneous with coal ; a distinguished 

 German naturalist and microgi*apher having absolutely denied it 

 to the author last summer, placing rather the first appearance of 

 Diatoms at an infinitely more recent period. The only mention 

 which came under my notice of the existence of Diatoms in coal 

 was a quotation from Acadian Geology by the distinguished American 

 naturalist, Dr. Dawson, referred to by Professor Huxley in a lecture 

 given by him On the Formation of Coal. To prove the assertion 

 that coal is not a subaqueous, but simply a sub-aerial formation, 

 Dawson, amongst other arguments, says that " with the exception 

 perhaps of some Pinnularice and Asterophyllites, there is a remark- 

 able absence from the Coal-measures of any form of properly 

 so-called aquatic vegetation." 



On reading that quotation my curiosity was aroused in the highest 

 degree ; because, whilst ardently pursuing the study of Diatomacese, 

 a strong conviction of their remote antiquity had fixed itself in my 

 mind. 



My wishes upon this subject were not influenced by any vain 

 sentiment, but I felt the importance of such an argument in es- 

 tablishing a principle set forth by me on several occasions. Having 

 discovered that in salt, fresh, and brackish waters the Diatomaceaa 

 (together with sea-weeds and vegetables of a higher order) de- 

 compose the carbonic acid under the action of the sun's raj's, and, 

 assimilating the carbon, set free the oxygen which is the chief and 

 indispensable element in animal respiration ; and having experi- 

 mentally found out that Diatoms, far from sustaining injury from 

 the presence of animal substances in a state of decomposition, rather 

 derive benefit from them — restoring, in short, the water itself to its 

 original state of purity ; I deduced from this the inference that in 

 nature the first appearance of Diatomacese must have coincided with, 

 if not preceded, the first moments of the existence of the primitive 

 animal inhabitants of the water. The last time I expressed this 

 opinion 1 added that sooner or later some rocks of Palaeozoic age 

 would, without fail, be met with to furnish indubitable proof of the 

 presence of Diatomaceae contemporaneous with the first animals that 

 lived in the waters. But I was very far from thinking that only a 

 few days after I had littered this prognostic it would be actually 

 verified. In a small residue collected from the incineration of a 

 fragment of coal (given me as coming from Liverpool), carefully 

 handled and placed for microscopic inspection, my satisfaction 

 may easily be imagined when several Diatoms, perfectly distinguish- 

 able, presented themselves in the field of the microscope. In this 

 way I was enabled to prove with all certainty what I had premised, 

 viz. that Diatoms vegetated in the Carboniferous period, that is to 

 say, with the earlier forms of animal life in the Palceozoic ages. 



