374 THE CANADIAN NATURALIST. [June 



characters are almost entirely obliterated. The leaves also are 

 nearly as abundant as those of Sigillaria in the coal-shales. They 

 can readily be distinguished by their strong angular midrib. 



I figure, in illustration of the genus, all the parts known to me 

 of L. Acadianus. (Fig. 171.) 



ON OZONE. 



A SOMERVILLE LECTURE IN 1866. 

 By Charles Smallwood, M. D., LL.D., D.C.L. 



What is Ozone ? Again, and perhaps, a q-uestion of greater 

 import — more especially at the present time — What is the 

 peculiar action and atmospheric influence, during Cholera and 

 some other of those diseases, usually called Epidemics ? This 

 subject has engaged the attention alike of the chemist, the 

 physician and meteorologist ; to each it has presented a prolific 

 field for investigation and research, and the subject becomes at 

 the present time of still greater importance from the existence of 

 cholera on the continent of Europe. As to whether cholera 

 may visit us or not, I shall not speculate, but content 

 myself simply to lay before you some points of interest in relation 

 to a powerful and subtile agent, a component of our atmosphere, 

 and which, from numerous observations, has been found to 

 possess a wonderful influence over some diseases, and to exert 

 some peculiar action on the lives of animals and vegetables. 



The nature and composition of the atmosphere was long- 

 involved in mystery ; its properties were not ascertained until 

 chemistry and other branches of natural science were considerably 

 advanced. 



The discovery of oxygen, by Priestly, was the first-fruits of 

 modern chemistry; and after its properties have been in- 

 vestigated for so many years, and ^in so ample and varied a 

 manner, we are only just now beginning to find out how utterly 

 io-norant we are of its real nature ; — a substance which is the very 

 breath of life for all created beings, both animal and vegetable, 

 which inhabit and propagate on our globe. 



In furtherance of our views on this subject, let us notice the 

 progress of Electrical science, one which now takes its rank 

 among the most important branches of natural philosophy, and 



