136 Analyses of Books, [Feb. 



position, and its being confinerl to the top of the hills, probably 

 belongs to the newcbt iioetz trap. 



Col Imrie accounts lor this disappearance of the t^reen-stftne, 

 by currents of water which formerly tiowed over this district frona 

 east to west ; and he points out traces of these currents, in scratches 

 still remaining on the surface of the green-stone, and in the parti- 

 cular configuration of the hills. This is the ingenious speculation 

 of Sir James Hall, to which he has given plausibility by his usual 

 industry and address. But it is a very hazardous speculation, the 

 sources of mistake being almost innumerable, and the means of 

 correcting error very scanty. The speculation seems to have ori- 

 ginated with Saussure and Dolomieu, who, however, were never 

 able to make much of it. 



Col. Inn'ic has entered into some discussions respecting the ig- 

 neous or aqueous origin of green-stone. He has shown, by an 

 example fvoai the neighbourhood of Carthage, that columns may 

 be forjncd in substances deposited from water; and by an example 

 from tlie Lipari islands^, that they may be formed likewise from 

 lav'a. Obsidian and pumice lie considers as of volcanic origin. 

 1 should like much to know, whether the composition of the ob- 

 sidian found in Hungary be the same with that found in Iceland, 

 Lipari, and the Peak of Tenerltl'e. It is very likely that they 

 would be found to differ ; and that the dispute about the aqueous or 

 igneous origin of this mineral, has originated from giving the same 

 iiame to two different species. 



o. Clieh'iical Aiialyiis of a Specimen of Mo'^netic Iron Or 9 from 

 Greenland. By Thomas Thomson, M . D. F. R. S. L. and E.— The 

 analysis of the ores of iron constitutes one of the most difficult 

 parts of mineraiogical chemistry. The present example, cona- 

 pared with the Swedish ores lately analyzed by Berzelius, is suffi- 

 cient to show, that more than one species of magnetic iron ore 

 exists. Berzelius's ores were combinations of black and red oxides 

 of iron. My ore contained titanium, and fiom the quantity of 

 red oxide of iion obtained, ( i2G-5 from 100 of the ore,) it is obvious 

 that part of the iron must liave been in the metallic state. This is 

 further confirmed by the effervescence of the ore with muriatic 

 acid, 'i'he speculation, that the ore consists of an unknown pro- 

 toxide of iron, is supported by too slight analogies to be admitted. 



4. Descripiion of a Sword Fish found in the Frith of Forth, in 

 June, 1811. By William Elford Leach, Esq. F.L.S. W.S. ^c. 

 — To this species. Dr. Leach gives the name of Xiphias Ronde- 

 Ictii, be(;ause he thinks it was first discovered and described by 

 Rondel'Jtius. The Xiphias Gladius is likewise probably found in 

 the Frith. 



5. Sor?ie Observations on ike Genus Sqiicdiis of Linn<Tf/f, with 

 Descriptio?}s and outline Figures of two British Species. By \Villiam 

 Elford Leach, Esq. F. L.S. W.'S. &c.— Dr. Leach divides tiie 

 family of the squalinidae into four genera, as follows : — 



