712 



SCIENCE. 



[N. S. Vol. XVII. No. 435. 



ruggedness of the limestone belt in which the 

 cave lies, are entirely out of harmony with 

 the existence of mastodons, elephants and 

 tapirs. Stream-worn pebbles occur in the 

 canon of the McCloud, at Baird, as high as 

 750 feet above the river. The deposit in the 

 cave dates from a time when the river flowed 

 at a higher elevation than it does now, but 

 not at the 750-foot point, otherwise the cave 

 would have been flooded, and of this there is 

 no evidence. At this time the cave was, in 

 part at least, an open fissure receiving ma- 

 terial washed in during the wet season. 



There are three well-defined terraces in the 

 canon of the McCloud. The lowest of these 

 is about 25 feet above the mean low-water 

 level of the river. A second terrace occurs 

 about 30 feet higher. The best-developed 

 terrace is about 75 feet above the stream. The 

 cave deposit was probably formed before these 

 terraces were cut, since a comparatively short 

 time has been required for the river to cut 

 down to its present level from the level of 

 the upper terrace. This terrace is rock cut 

 with a thin veneer of gravel on its surface. 

 When the river flowed at the level of this 

 terrace, it is not believed that the region was 

 topographically adapted to the existence of 

 tapirs and the large proboscideans, except 

 perhaps along the stream. 



A full report embodying the results of fur- 

 ther work on the cave and descriptions of new 

 species will appear later, in the Publications 

 of the University of California. 



Wm. J. Sinclair. 



University of California, 

 Berkeley, California. 



CURRENT NOTES ON METEOROLOGY. 



HELM CLOUD IN THE BLUE EIDGE OF NORTH 

 CAROLINA. 



Whbn wind is forced to cross a mountain 

 ridge, standing waves may be produced in the 

 air currents to leeward of the ridge. If the 

 involuntary ascent of the air is sufficient to 

 bring about condensation, clouds are formed 

 in the ascending portion of these waves. The 

 best known of these clouds is that called the 

 Helm Bar, which is frequently observed when 

 a damp easterly wind blows over the Cross Fell 



range, in northwestern England. Attentive 

 observation in mountainous districts ought to 

 bring record of the occurrence of many such 

 clouds in diSerent parts of the world. W. 

 M. Davis (Bull Qeogr. Soc. Phila., III., No. 

 5, 1903) calls attention to a similar cloud 

 which he observed during a recent field trip 

 to the Blue Ridge in North Carolina. On a 

 morning with a clearing northwest wind, while 

 standing on Mt. Mitchell, he noted that a roll- 

 ing helm cloud was formed above the Blue 

 Eidge escarpment. The cloud held its place, 

 continually forming and dissolving, for more 

 than an hour, while many detached fragments 

 of the cloud floated away and disappeared 

 during this time. This is the first mention 

 of the occurrence of helm clouds in this sec- 

 tion. 



METEOROLOGICAL PHENOMENA OP VOLCANIC 

 ERUPTIONS. 



An ascent during an eruption of the vol- 

 cano Purace, near the city of Popayan, the 

 capital of the Department of Cauca, in the 

 Republic of Colombia, is described by R. B. 

 White in the Scottish Geographical Magazine 

 for February. The eruption occurred in Oc- 

 tober, 1869, and Mr. White was requested by 

 the natives to ascend the mountain during the 

 eruption, in order that he might report to 

 them regarding the danger that threatened 

 the neighborhood. A number of interesting 

 phenomena were noted, one of which was the 

 sudden tremendous flood which came down 

 the river Cauca, produced by the almost in- 

 stantaneous melting of ' at least 8,000,000 

 cubic feet of snow that lay on the mountain.' 

 The column of steam reached a height of 

 three miles, having the appearance of immense 

 cumulus clouds, and spreading out at the top 

 like the crown of a great tree. (Similar mush- 

 room-shaped clouds were noted, and photo- 

 graphed, during the Mont Pelee eruptions of 

 last summer). During the night frequent 

 torrents of mud and rocks rushed down the 

 mountain sides. These, Mr. Wliite believes, 

 came from the melting of the heavy snow 

 which had resulted from the condensation of 

 the great volumes of vapor thrown up from 

 the crater. This snow melted rapidly on the 



