Notices respecting Neiv Books. 67 



I shall endeavour to find out the circumstances under which 

 this complete discoloration of the ligneous matter of the 

 leaves takes place, for this is interesting in a technical point 



of view. 



Postscript by Dr. Ehrenberg, 



The very meritorious attention of Prof. Kersten to this 

 leather-like substance has recalled to ray mind the subject 

 formerly touched upon p. 119 of my work on Infusoria, but 

 particularly so in relation to the meteoric paper of Courland * 

 that I could not omit submitting it to a microscopic exami- 

 nation. With regard to this meadow-leather of Schwarzen- 

 berg, it consists most distinctly of Conferva capillaris, Con- 

 ferva punctalis and Oscillatoria limosa, forming together a 

 compact felt, bleached by the sun on the upper surface, and 

 including some fallen tree leaves and some blades of grass. 

 Among these confervas lie scattered a number of siliceous in- 

 fusoria, chiefly Fragilariae and Meridian vernale. I have ob- 

 served sixteen different sorts of such siliceous infusoria, be- 

 longing to six genera ; besides these I have found three sorts 

 of infusoria with membranous shields, and dried specimens of 

 Anguillula fluviatilis. 



Thus the silica is quite explained, as well as a part of the 

 iron, of which last another part, as also the manganese, may 

 arise from a little dust which lies in irregular particles with the 

 infusoria among the confervae. I have treated more circum- 

 stantially, before the Academy of Sciences, of the meteoric pa- 

 per of 1686, which I found to be similar to this in composi- 

 tion. 



XIV. Notices respecting New Books. 



Chemistry of Organic Bodies. Vegetables. By Thomas Thomson, 

 M.D., F.R.S., S(C., and Regius Professor of Chemistry in the Uni- 

 versity of Glasgow. 



THE object of the present volume, we are informed by its autlior, 

 is to lay before the British chemical public a pretty full view of 

 the present state of the chemistry of vegetable bodies ; and he truly 

 observes, that "this branch of the science has made so much progress 

 of late years, that a very wide and inviting field has been laid open. 

 Several hundred new substances have been either discovered, or 

 their characters have been determined with such precision, and their 

 composition investigated with such accuracy, as to give a pretty ac- 

 curate idea of their constitution, and of their connexion with each 

 other. These ultimate analyses, with very few exceptions, have 

 been all made upon the continent, and chiefly in Germany and in 



* A translation of Dr. Ehrenberg's notice on the meteoric paper of 1686 

 has appeared in the Annals of Natural History, vol. iii. p. 185. 



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