Vlll PREFACE. 



tions which contain scientific treatises by a variety of hands, 

 such as Transactions of Societies, Journals, Magazines and 

 Encyclopaedias. The several treatises of which these periodicals 

 consist, as far as they relate to our subject-matter, are regi- 

 stered alphabetically under the author's name in the second 

 part of the work. This vast undertaking can at present be 

 only partially executed, from the difficulty before alluded to, 

 of obtaining access to all the periodicals enumerated in the 

 first part. So far however as the compilers have been able to 

 perform this part of their project they have done it conscien- 

 tiously, taking such periodicals as were within their reach, 

 and faithfully extracting the titles of the memoirs which they 

 contain. The titles of all detached and independent works 

 are also inserted in the alphabetical series, so that under the 

 name of each author will be found a complete list of all his 

 writings in these departments of natural history. 



As already stated, this compilation is professedly limited to 

 scientific Zoology and Geology, yet it must be admitted that 

 M. Agassiz has inserted, rather too indiscriminately in my 

 opinion, many titles of works which are only remotely con- 

 nected with those subjects. Had I been the sole compiler 

 instead of the editor of the work, I should, for the sake of 

 rendering it less bulky, have excluded all merely popular and 

 elementary essays, all treatises on Human and Morbid Ana- 

 tomy, on Ethnography, on Domestication of Animals and the 

 Veterinary Art, on pure Mineralogy and Crystallography, on 

 Mining and Metallurgy, and all popular Voyages and Travels. 

 Too many of such works have however crept into the Cata- 

 logue, and I, as editor, did not, except occasionally, feel jus- 

 tified in excluding them. To have erased a work from the 

 list merely because its title appeared irrelevant to our especial 

 subjects would have been highly improper, and to have con- 

 sulted the original work in all doubtful cases would not only 



