578 



SCIENCE 



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



in the late afternoon, the second reversal 

 would be brought about. The down-valley 

 current would then set in, taking the smoke 

 back with it. 



To the writer who was at the time engaged 

 in the topographic survey of the valley this 

 daily smoke invasion was, it may be imag- 

 ined, a source of no little annoyance; for, 

 while it lasted, it precluded all long-distance 

 graphic triangulation across the valley, the 

 only means whereby the host of peculiar cliff 

 details, so characteristic of the Tosemite Val- 

 ley, could be located. Nor was it a matter of 

 a day or two; with a provoking regularity 

 rendered possible only by the general absence 

 of disturbing winds and cloudy skies, typical 

 of the region, it continued for four long 

 months with scarce an interruption. 



No doubt intimately related to the rhythmic 

 reversals of the lengthwise air current is the 

 period of placidity of Mirror Lake. The sur- 

 prised and usually vexed tourist who finds he 

 must get up an hour before sunrise if he 

 wishes to see the mirror at its best, little sus- 

 pects that what he has undertaken to do 

 really amounts to keeping an appointment 

 with the early-morning reversal of the air 

 current, and that punctuality on his part is 

 vital because of the almost momentary brief- 

 ness of the phenomenon. Yet such is actu- 

 ally the case. The stillness of the water sur- 

 face sets in as the down- valley draft dies out; 

 but as soon as a sufficient amount of cliff sur- 

 face has been insolated in Tenaya Canyon, 

 the upward movement becomes general, and a 

 faint tremor once more steals over the lake. 

 That its placidity is less perfect with the 

 afternoon reversal is probably due to the rela- 

 tive suddenness with which that reversal takes 

 place and the almost immediate strength of 

 the downward currents in a narrow steep- 

 walled chasm like Tenaya Canyon. 



There is a certain appropriateness, finally, 

 in likening the nocturnal down-valley current 

 to a stream. For not only does it follow the 

 bottom of the valley trough as a channel, 

 but it also receives tributaries from the side 

 valleys. In the case of the Tosemite Valley, 

 the parallel is the more complete, as each trib- 



utary air current literally plunges, water-fall- 

 like, from the mouth of its hanging valley. 

 Few visitors to the valley, probably, are aware 

 of the existence of these — shall we call them 

 " air-falls" ? — nevertheless they are by no 

 means imaginary, as one may readily iind out 

 to his satisfaction by ascending either the 

 Tosemite Falls trail or the Nevada Falls trail 

 in the evening. The writer had occasion to 

 do so many times in returning to his high- 

 level camps above the valley, and the un- 

 pleasant memory of the chilling down drafts 

 that poured upon him on these evening trips 

 has not yet lost its vividness. 



Francois E. Matthes 

 Washington, D. C. 



the effect of asphyxia on the pupil^ 

 Over a year ago I reported^ that CO, gas 

 produced a practically maximal constriction 

 of the pupil, both in the intact frog and in 

 excised bulbi, and I stated that this behavior 

 of the frog's iris was interesting because 

 asphyxia in mammals produces chiefly dilata- 

 tion. This latter statement gave surprise to 

 Drs. C. C. Guthrie, F. V. Guthrie and A. H. 

 Ryan and they write in a recent issue of 

 Science' that " in all animals observed, only 

 momentary or no dilatation of the pupil occurs 

 during the first stage of rapid asphyxia (...), 

 and that as a rule a very marhed constriction 

 of the pupil occurs during this stage." It must 

 be noted that these authors speak only of the 

 first stage of asphyxia, the stage of hyper- 

 pnoea, and do not mention at all the second 

 and third stages, where true asphyxia has de- 

 veloped. Had they pushed their experimental 

 investigations a little farther, they would have 

 found the marked dilatation of the pupil which 

 occurs in mammals during the second and 

 third stages of asphyxia. This well-known 

 dilatation of the pupil is more pronounced and 



^A reply to Drs. C. C. Guthrie, F. V. Guthrie 

 and A. H. Ryan. (From the department of 

 physiology and pharmacology of the Rockefeller 

 Institute. ) 



^ Amer. J. of Physiol., 1908, XXIII., p. xvi; see 

 also report of a demonstration, Proc. of the Soo. 

 for Exp. Biol, and Med., 1908, VI., p. 49. 



"Science, March 11, 1910, XXXI., p. 395. 



