Decembee 11, 1908] 



SCIENCE 



839 



measures were successful, and we discussed what 

 had ailed us. According to George, our hats, 

 becoming damp, had been charged like Leyden 

 jars and, growing overcharged, had unloaded into 

 our heads. 



I have made no attempt to change and 

 render more dignified the somewhat informal 

 character of this chronicle. It was written a 

 few hours after the experience in the hail- 

 storm which had not reached the valley where 

 our camp was. Wheil we returned there, we 

 found the aspect of summer as unchanged as 

 when we had left it in the morning. On the 

 top of the mountains the hail stayed only a 

 few hours beneath next day's sun. As we con- 

 tinued our hunt for mountain sheep, there was 

 not a trace of it. 



Owen Wister 



Philadelphia, 



November 21, 1908 



began to form on the range, as a result of the 

 adiabatic cooling of a northwesterly air-cur- 

 rent forced to rise in crossing the obstruction. 

 They grew rapidly, very soon uniting into a 

 long cloud cap over the whole visible length of 

 the range (five or six miles) and trailing off 

 to leeward from its southern end to a dis-- 

 tance of two — a cloud seven or eight miles 

 long in all. The ragged end at intervals sent 

 off scraps resembling fracto-nimbus, which 

 were gradually dissipated as they drifted away 

 from the parent cloud. 



The spectacle of a cloud-waterfall over 

 Bridger Peak, the highest portion of the range 

 visible from camp, was nothing short of 

 magnificent. Enormous billowing masses 

 surged one after another across the peak, 

 cascading down the leeward slopes and vanish- 

 ing in succession as a result of adiabatic 

 warming. 



A NOTABLE CLOUD BANNER 



To THE Editor of Science: Early in July, 

 1907, an exceptionally fine cloud banner 

 formed on the southern end of the Bridger 

 range in southwestern Montana. This range, 

 an isolated outlier of the Eockies, trends north 

 and south, thus acting as an obstruction to 

 frequent squally and showery northwest winds 

 which approach it across the Gallatin Valley 

 to the westward. On the occasion mentioned, 

 the writer was camped six miles east of the 

 southern end of the range. Brisk thunder 

 showers from the northwest had occupied 

 most of the afternoon until about five o'clock, 

 after which the sky remained overcast with 

 nimbus and occasional flying patches of 

 fracto-nimbus. Presently little cloud caps 



There was no associated standing cloud to 

 leeward. Either the obstruction offered by the 

 range to the passage of the air-current was 

 insufficient, or the current itself was too weak, 

 to set up a secondary wave high enough to 

 raise the air again to condensation level. In 

 this respect the Bridger cloud differed from 

 the clouds over the Cross Fell range in north- 

 western England, where the famous Helm 

 Bar often tops the crest of a long standing 

 wave to leeward of the mountains. Its occur- 

 rence is described by Brunskill in the Quart. 

 Jour. Boy. Met. 8oc., X., 1884, 267-275. Pro- 

 fessor W. M. Davis reports a similar case for 

 the Cevennes in the M. Z., XVI., 1899, 124r- 

 125. 



