31 



shining black mass, with exactly the appeai'ance of coal and the scaly 

 structure which coal possesses. Coal, vinder a pressure of 6,000 

 atmospheres, was moulded with ease. Precipitated alumina, dried at a 

 temperature of 140*^, became fluid under a pressure of 5,000 atmospheres. 

 Many chemical reactions were also induced by pressure, for instance, 

 copper filings and sulphur, when mixed together and submitted to 

 pressure, united, forming a crystalline black sulphide of copper. A 

 mixture of chloride of mercury and copper filings at a pressure of 5,000 

 atmospheres underwent a change into chloride of copper and mercury. 

 Amorphous iodide of mercury under a pi'essure of 4,000 atmospheres 

 became compacted into a block, showing, under the microscope, a mass of 

 translucent crystal fragments. It thus appears that great pressure alone 

 can, in certain cases, at least — 1st, soften, and even melt solid bodies 

 (coal, peat, alumina) ; 2nd, crystallize bodies capable of assuming 

 crystalline form (iodide of raercui'y) ; 3rd, induce chemical reactions 

 (chloride of mercury and copper filings). All regions composed of 

 crystalline schists show in the complicated folding and twisting of their 

 strata evidence of having been submitted to tremendous pressure. In 

 great pressure we probably have a very simple and beautiful explanation 

 of many cases of regional metamorphism. In order to be so altered, 

 however, the original rocks would have to contain all the elements 

 required for the production of the resulting crystalline schists, since 

 by pressure alone the change could only be one of diagenesis. 



FISHES OF THE OTTAWA DISTRICT. 



H. B. Small. 



Note. — The nomeyiclature adopted is taken, from Jordan and Gilheris 

 latest synopsis of the Fishes of N^orth America. 



The fishes of Canada and especially of this district, present a field 

 of observation as yet very partially travelled, and one that will repay 

 minute investigation. Not only are there doubtless species as yet 

 unobserved and und escribed, but a more careful desci'iption and com- 

 parison of those already noted will contribute much to the progress . of 



