80 



SCIEJSrCE. 



[Vol. VIII., No. 181 



frontal moraines. That map is entitled 'Verbrei- 

 tungsweiseder Alpen-fiindiing-e,'and its author is the 

 modest and very able geologist, A. Escher von der 

 Linth. 



Since 1850, Gastaldi for Piemont, Chantre and 

 Falsan for France, and A. Favre for Switzerland, 

 have given maps of the ancient extension of the Al- 

 pine glaciers, which render Guyot's maniiscript map 

 obsolete and valueless, except as an historical docu- 

 ment. 



To finish this already too long revievs^ of glaciers 

 and glacialists, I will add, that, after the three origi- 

 nal memoirs of Venetz, de Charpentier, and Agassiz, 

 of 1833, 1834, and 1837, the other important works 

 and landmarks in the discovei'ics and exposition of 

 the glacial question are, by order of data, 1% ' Theo- 

 rie des glaciers de la Savoie,' by the ChanoineEendu 

 {September, 1840) ; of this most important and excel- 

 lent work, Tyndall said to me at the Geneva meeting 

 of the Swiss naturalists in 1865, " If Eendu had been 

 trained and educated as a physicist, he would have 

 left nothing for others to do;" 2\ 'Etudes sur les 

 glaciers,' by Louis Agassiz (October, 18-10); 3", ' Essai 

 sur les glaciers,' by Jean de Charpentier (Oct. 31, 

 1840 ; issued in December, 1840, with the date on the 

 titlepage of 1841) ; 4", ' Travels through the Alps of 

 Savoy,' by James D. Forbes (1843 ; second edition, 

 1845) ; 5°, ' Nouvelles etudes et experiences sur les 

 glaciers actuels,' by Louis Agassiz (November, 1847); 

 6°, ' The glaciers of the Alps,' by John Tyndall (1860). 



Venetz was personally known to but few savants. 

 I will add that he was a Valaisan engineer of great 

 skill. He had the charge of rectifying and embank- 

 ing the Ehone in the cantons of Valaisaud Vaud, from 

 Sion and Martigny to the lake of Geneva, — works 

 which he executed most successfully. Accustomed 

 to observe all that relates to the freshets of moun- 

 tain torrents and glaciers, a spectator of the great 

 ■'debacle de Bagnes' in 1818, he and his friend de 

 Charpentier put a stop to the constant ravages of the 

 Getroz glacier and the Dranse Eiver, an affluent of 

 the Ehone. 



Venetz's modesty was extreme, and verging on 

 great timidity, due perhaps, in part, to the infirmity 

 so common in the Valais, and from which he was a 

 sufferer. Not educated as a scientific man, but only 

 as a road engineer, be did not possess the scientific 

 method of marshalling and classifying facts and ob 

 servations. But Venetz found in his friend de Char- 

 pentier the best man to systematize and construct a 

 new science. In that respect de Charpentier, by his 

 knowledge and education, was the equal and rival of 

 his friends Alex, de Humboldt, Leopold de Buch, and 

 Elie de Beaumont ; and the association of Venetz with 

 him was most happy and successful. Both without 

 ambition, lovers of nature and truth, they created to- 

 gether what may be called cow one of the most inter- 

 esting branches of geology and physical geography. 



Jules Marcou. 

 ■Cambridge, Mass., July 7. 



As clearly indicated by Mr. Gilbert, it is evident, 

 that, according to the conditions of exposure, the 

 influence of the wind must tend sometimes to in- 

 crease, and at other times to diminish, the pressure 

 within the building in which the barometer is placed. 

 Now, all of Mr. Clayton's experiments seem to indi- 

 cate a lowering of the barometer-readings within 

 the building. Perhaps he may be able to verify the 

 deductions of theory by so arranging the conditions 

 of exposure as to secure the opposite effect, and thus 

 obtain a complete verification of his induction. If 

 these opposite effects can be vei'ified by experiment, 

 while establishing the influence of wind as a true 

 cause of barometric fluctuations, they would render 

 it extremely difficult to apply a correction correlated 

 with the velocity of the wind, except under well- 

 defined conditions of exposure. 



While seeking for possible causes of fluctuations of 

 the barometric column in relation to wind-velocity, 

 it may be well to recall the idea first broached by 

 Hawksbee near the beginning of the last century, 

 and more distinctly urged by Sir John Leslie, that 

 the barometer is depressed by wind in consequence 

 of the centrifugal force due to the horizontal current 

 of air (Daniell's ' Elements of meteorology,' vol. i. 

 pp. 4-9, London, 1845); for although Professor 

 Daniell's criticism of Professor Leslie's theory is 

 quite just, in so far as it relates to the idea that the 

 effect would be ' accumulated by a long series of 

 deflections,' yet the main fact, that the tendency to 

 rectilinear motion would give rise to a centrifugal 

 effect, remains a vera causa tending to depress the 

 mercurial column. 



A simple calculation shows, however, that the 

 radius of curvature is so large, or the deflection from 

 a tangent is so small, that a horizontal wind of 60 

 miles per hour, or 88 feet per second (assuming the 

 whole thickness of the atmosphere to be involved), 

 would lower the mercury in the barometric column 

 only about 0.00875 of a millimetre, or 0.00034 of an 

 inch, — an amount so small as to be far within the . 

 limits of observational error, and therefore quite in- 

 adequate as an explanation of the phenomenon. 



John LeConte. 

 Berkeley, Cal., July 1.3. 



Barometer exposure. 



It is gratifying to find that my brief letter calling 

 in question the influence of wind on the indications 

 of indoor barometers has elicited very satisfactory 

 responses from Messrs. Gilbert and Clayton {Science, 

 vol. vii. pp. 571, 572 ; and vol. viii. p. 14). There is 

 one point, however, on which evidence is still want- 

 ing to fortify Mr. Clayton's induction. 



Bright lines in the spectrum of /? Lyrae. 



A short study of the spectrum of p Lyrae presents 

 the following bright lines as existing in her atmos- 

 phere. A portion are probably also found in the 

 solar atmosphere. Eeferred to bv their numbers in 

 Young's catalogue, they are, 2, '3, 5, 22, 36, 41, 49, 

 (58-59), 69, 74, 86, 100, (105-106), 115, (138-139), 

 (140-141), 181, 189, 193. 198, 208, 248, (260-261), 

 267,(272-2731). Another portion find no place, or 

 are infrequent, in the solar atmosphere, and, re- 

 ferred to by their approximate wave-lengths, are 

 59549, 58398. 57967, 57544, 56305, 55829, 54811, 

 .51355, 51013, 50858, 50582, 49582, 47939, 47660, 47487,. 

 46879. 45203, 43123. 



Each of these appear in at least 40 per cent of the 

 observations ; none appear in more than 70 per cent. 

 A number more are suspected, but are not clearly 

 separated. 



At present there would seem to be a connection 

 between the variability of the star and the lines 

 present in the spectrum ; but on this point the obser- 

 vations are not final. O. T. S. 



New Haven, July 17. 



