394 



SCIENCE 



[N. S. Vol. XXXI. No. 79S 



the mountain. Of these the more important 

 were the general climatology of Mount Eose, 

 the relation of climate to the plant environ- 

 ment, the relation of timher to the conserva- 

 tion of snow, and the frost forecasting from 

 the summit. With such a record for its short 

 life, and with amhitious plans for the future, 

 progress is certain to be the result. Having 

 recently been assured of further support by 

 the office of experiment stations of the na- 

 tional government, the zealous workers are 

 almost certain to produce results which will 

 he of great value to meteorology in general 

 and to the agricultural interests of the Great 

 Basin in particular. 



Andrew H. Palmer 

 Bltje Hill Obseevatoey, 

 Hyde Paek, Mass. 



CONCERNma THE DATE OF TEE LAMARCK 

 MANUSCRIPT AT HARVARD 



A CURIOUS mistake has found its way into 

 M. Landrieu's "Life of Lamarck" regarding 

 the probable date of the Harvard manuscript 

 to which I referred in the March number of 

 the American Naturalist. In this article I 

 had stated that the " Manuscrits de Lamarck " 

 were " hrought together in a volume, the bind- 

 ing dating 1830-40," and that in this little 

 volume there was " a table of contents, prob- 

 ably in the hand of the early owner [this 

 does not mean the author^ of the manu- 

 script." Also that " it will he noted that the 

 papers were collected before 1S35, the year 

 of the appearance of the second edition of the 

 'Animaux sans Vertebres,' " because in the 

 table of contents, referred to above as " in the 

 hand of the early owner " " it is stated that 

 the drawings will form part of the second 

 edition " of that work. 



Now M. Landrieu remarks in perfect seri- 

 ousness that I have given the probable date 

 of the writing of the manuscript " as before 

 1835," at which time, as he notes, " Lamarck 

 had been dead six years, after ten years of 

 total blindness!" So I must now smilingly 

 protest that I was aware of the date of 

 Lamarck's death, and even when his eyesight 

 failed him — in fact I mentioned the latter 



date, as 1818, in the same Naturalist paper 

 (p. 148) which my colleague has so imper- 

 fectly read. The year 1835 is but a landmark 

 in the Harvard manuscript, since it was at 

 that time or somewhat before that time that 

 its five component parts were brought together 

 in a little volume by the " early owner," who 

 may well have been an editor of the second 

 edition of the " Animaux sans Vertebres." 

 H, moreover, my good friend M. Landrieu had 

 interpreted the Naturalist paper carefully, he 

 might have discovered that I have given the 

 probable dates of various parts of the Har- 

 vard manuscript as prior to 1818, " the year 

 in which Lamarck's eyes failed him." So, 

 after all, M. Landrieu's estimate of the date 

 of these manuscripts and my own do not dif- 

 fer widely. He gives the dates between 1810 

 and 1820 — thus he is even less conservative 

 than myself, for he assumes that Lamarck 

 may have continued to write his papers pro- 

 pria manu even after his eyesight failed. 

 Bashford Dean 



SPECIAL ARTICLES 

 the interference of the reflected diffracted 



AND THE diffracted REFLECTED RAYS OF A 



PLANE TRANSPARENT GRATING, AND ON 



AN INTERFEROMETER 



If parallel light, falling on the front face 

 of a transparent plane grating, is observed 

 through a telescope after reflection from a 

 rear parallel face the spectrum is frequently 

 found to be intersected by strong vertical 

 interference hands. Almost any type of 

 grating will suffice, including the admirable 

 replicas now available, like those of Mr. Ives. 

 In the latter case one would be inclined to 

 refer the phenomenon to the film and give 

 it no further consideration. On closer inspec- 

 tion, however, it appears that the strongest 

 fringes certainly have a different origin and 

 depend essentially on the reflecting face be- 

 hind the grating. If, for instance, this face 

 is blurred by attaching a piece of rough wet 

 paper, or by pasting the face of a prism upon 

 it with water, so as to remove most of the 

 reflected light, the fringes all but disappear. 

 If a metal mirror is forced against the rear 



