184 On Canadian Caverns. 



tionary masses in tertiary clays,* and is sometimes mingled with 

 a silicate having the composition of allophane. This frequent 

 occurrence of alumina still retaining a portion of sulphuric acid, 

 confirms the view which we have elsewhere expressed, that solu- 

 tions of native alums have by their decomposition furnished the 

 alumina for many of the mineials in question, while the con- 

 ditions under which this base is taken into solution by organic 

 matters, still require investigation. The careful examination of 

 unaltered sedimentary deposits, is calculated to throw great ad- 

 ditional light upon the origin of the crystalline rocks. 



ARTICLE XII. — On Canadian Caverns. By George D. Gibb 

 M.A., M.D., F.G.S. London, England. 



(Extracts from a Paper read before the British Association, Sept. 1859J 



The prominent feature of a large portion of the province of 

 Canada is the presence of various limestone rocks belonging to 

 the Silurian formations. Until lalelv, the existence of caverns in 

 these rocks, as well as in those lying subjacent — namely, the 

 Laurentian of Sir William Logan, was almost unknown ; as, with 

 the exception of an isolated account here and there, no regular 

 description of any cavern had appeared. Owing to the labours 

 of the Canadian Geological Survey, and of several private individ- 

 uals, a number of caverns have been discoved at distances 

 remote from one another ; some of these have received but a pass- 

 ing notice in the publications of the Survey, and are not, there- 

 fore, useful as a means of reference. The present communication 

 it is hoped, will supply that deficiency, as in it I propose to embody, 

 short desciiptive accounts of all the caverns of Canada which are 

 known up to the present time. The details of some of them are 

 not so full as could be desired ; nevertheless, with all the available 

 sources of information within my reach, together with personal 

 observation in some, on the whole the general descriptions may be 

 relied upon as accurate, and as containing a correct account of 

 the geological formations in which they lie. 



The caverns of Canada may conveniently be divided into two 

 classes ; the first comprises those which are at the present time 

 washed by the waters of lakes, seas, and rivers, including arched, 



* In this connection we may notice apatelite, a basic persulphate of 

 iron, which occurs in conditions similar to alumiuite. 



