276 REVIEWS — GEOLOGICAL SURVEY OF CANADA. 



these deposits together tinder the common term of the Trenton group 

 or series. 



Mr. Sterry Hunt's contributions to the Report of Progress for 

 1857j comprise a continuation of his researches on the composition of 

 our magnesian hmestones and the formation of dolomites generally, 

 together with a valuable and very interesting communication on Fish 

 Manures. Pure dolomite consists of equal atomic proportions of car- 

 bonate of lime and carbonate of magnesia ; or, in 100 parts, of 

 CaO,C02 54.35, and MgOjCO^ 45.65. Very few of our magnesian 

 limestones, however, exhibit these exact proportions ; but Mr. Hunt, 

 availing himself of a reaction pointed out by Karsten many years 

 ago, has shewn that most of these consist of an admixture of carbonate 

 of lime and true dolomite. Whilst the latter compound resists the 

 action of cold acetic acid, or is but slightly attacked, carbonate of lime 

 is readily dissolved by that re-agent, and hence, a separation of the two 

 is easily effected ; the silica and other accidental matters being after- 

 wards removed from the dolomite by treatment with hydrochloric 

 acid. A portion of the carbonate of magnesia, in the majority of the 

 dolomites analysed by Mr. Plunt, is replaced by carbonate of iron, and 

 in some, also, by carbonate of manganese. Examples of magnesian 

 limestones containing a larger amount of magnesia than is required for 

 the production of a dolomite, although of not uncommon occurrence 

 in other countries, do not appear to have come under observation in 

 Canada. "With regard to Mr. Hunt's comprehensive and now appar- 

 ently well-established views on the origin and formation of dolomites, 

 we must refer our readers to the valuable paper communicated by that 

 gentleman to the last number of the Canadian Journal (page 184), 

 Mr. Hunt having greatly extended his experimental researches on this 

 subject since the date of the present Report. 



Mr. Hunt's remarks on the manufacture of fish-manures are of 

 great practical importance, and merit well the attention of our agricul- 

 turists. Fish have long been used as a manure in many parts of 

 Europe bordering on the sea, and more especially along the western 

 coast of France, in Scotland, and on the hop grounds of the English 

 counties of Kent, Sussex, and Hampshire. At Concarneau, in the 

 department of Finisterre in France, an establishment for the manufac- 

 ture of portable manure from the offal of sardines, caught extensively 

 off that coast, is in active operation. The process consists in exposing 

 the fish- offal for some hours to steam heat, pressing it afterwards ta 



