ACKNOWLEDGMENTS TO CORRESPONDENTS, FRIENDS 

 AND STRANGERS. 



Remarks. — This method of acknowledgment has been adopt- 

 ed, because it is not always practicable to write letters, where 

 they might be reasonably expected ; and still more difficult is it 

 to prepare and insert in this Journal, notices of all the books, pamph- 

 lets, &;c., which are kindly presented, even in cases, where such no- 

 tices, critical or commendatory, would be appropriate j for it is often 

 equally impossible to command the time requisite to frame them, or 

 even to read the works ; still, judicious remarks, from other hands, 

 would usually find both acceptance and insertion. 



In public, it is rarely proper to advert to personal concerns ; to 

 excuse, for instance, any apparent neglect of courtesy, by pleading 

 the unintermitting pressure of labor, and the numerous calls of our 

 fellow-men for information, advice, or assistance, in lines of duty, 

 with which they presume us to be acquainted. 



The apology, implied in this remark, is drawn from us, that we may 

 not seem inattentive to the civilities of many respectable persons, au- 

 thors, editors, publishers, and others, both at home and abroad. It 

 is still our endeavor to reply to all letters which appear to require an 

 answer ; although, as a substitute, many acknowledgments are made 

 in these pages, which may sometimes be, in part, retrospective. — 

 Eds. 



SCIENCE. FOREIGN. 



Das Naturell die Krankheiten, das Arztthum und die Heilmittel 

 der Urbewohner Brasiliens. Von Dr. K. Fr. Ph. v. Martins. Miin- 

 chen. From the Author. 



Chemical Gazette, London. Conducted by Wm. Francis. 



Verbreitung und Einflufs des Mikroskopischen Lebens in Siid 

 imd Nord Amerika. Ein vortrag von C. G. Ehrenberg. Berlin, 

 1843. pp. 137, folio, with plates. From the Author. 



Bericht iiber die zur Bekanntmachung geeigneten Verhandlungen 

 der Konigl. Preuss. Akademie der Wissenchaften zur Berlin, "for 

 1840, '41, '42, '43, and to April inclusive of 1844. From Prof. 

 Ehrenberg. 



The Medals of Creation, or First Lessons in Geology and in the 

 study of Organic Remains, by Gideon Algernon Mantell, LL. D. 



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