1 ) The select bibliography which follows is a great amplification of 

 the one which was published in an appendix to the author's Study of the 

 History of Science (p. 53-70, Cambridge, Massachusetts, 1936). In 

 spite of the fact that it is considerably larger than the list of 1936, it is 

 still very short when one takes into account the immensity of the field. 



It is based primarily upon the author's own library and that is not 

 only a cause of strength but also of weakness. No library is perfect and 

 one which like my own is used not only by myself but by many col- 

 leagues and students is bound to have lacunas. A not unimportant book 

 may have escaped my attention, because it was "out" when I examined 

 the shelf where it ought to have been or because it has been mislaid by 

 a careless scholar. Moreover, important books sent to me by the author 

 or publishers are given to collaborators for review in Isis. Sometimes, 

 I have replaced the book by buying a new copy of it, sometimes not, 

 when I had no particular need of it. In that case, there is no witness 

 left of its existence, except the review ( if the reviewer was faithful ) . I 

 am thus bound to rediscover it, because this bibliography is built sec- 

 ondarily upon Isis. This will give the reader an idea of its condensation. 

 For the items published in the seventy-five Critical Bibliographies must 

 number at least seventy-five thousand.'^^ 



2) The Bibliography is divided into four parts, and each of these 

 parts into 6-8 chapters (see Table of Contents). The chapters are not 

 mutually exclusive and parts of their areas overlap. It must thus hap- 

 pen that an item listed in one chapter is listed again in another chapter 

 or might have been listed. In some cases, duplication seemed more ex- 

 pedient than cross-reference. 



3) As this book is written in English and will be used mainly by 

 English-reading students, their needs were given priority. More Eng- 

 lish books are listed than non-English; when a non-English book was 

 translated into English, the English translation is listed, but the other 

 translations ( if any ) are not; if the non-English book was not translated 

 into English but, say, into French or German, that translation is listed for 

 the sake of readers more familiar with French (or German) than with 

 the original language. 



Many books originally published in England are also published in 



" Moreover, these 75,000 notes refer to books or papers published within the 

 last forty years, while the "First Guide" refers to the main pubhcations irrespective 

 of time. 



