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THE POPULAR SCIENCE MONTHLY 



period duriug which it has already been 

 proved bj Mr. Bucivland and Mr, Youl that 

 the development of sahiion may be safely 

 retarded by ice. A large quantity of the 

 ice surrounding the ova remained till the 

 end of the voyage, so that the temperature 

 of the ice-houses must have been kept very 

 low throughout the voyage. The cases in 

 which they were packed are described as 

 "sodden," so that they did not suffer from 

 dryness. Probably want of ventilation 

 caused the failure of the experiment. 



Ancient Glaciers of the Sierra McTada at 

 Lake TahoCi In the American Journal of 

 Science for August is an interesting paper, 

 by Prof. Joseph Le Conte, on the ancient 

 " Glaciers of Lake Valley," in which is 

 situated the well-known and beautiful Lake 

 Tahoe. The great glacier which filled all 

 the lower part of the valley had its source 

 in the snow-fountains among the mountain- 

 peaks at its southern end. The valley is 

 a trough between two ridges of mountains 

 near the top of the Sierras. It is 20 miles 

 wide, 50 miles long from north to south, and 

 is 3,000 to 3,500 feet deep ; its lower half is 

 filled with the waters of Lake Tahoe. This 

 lake occupies an area of about 250 square 

 miles, and is 1,640 feet deep. 



On either side of the lake are mountains, 

 but those which still show best the glacial 

 sculptu rings are on the westerly side. Some 

 of these rise 3,000 feet above the level of 

 the lake, and are between 9,000 and 10,000 

 feet above the level of the sea. The surface 

 of the lake is at nearly as great an elevation 

 above tide as the summit of Mount Washing- 

 ton. The ice at its greatest development 

 filled the valley a vast 7ner de glace to a 

 height of 300 or 400 feet above the present 

 lake-level, and was therefore about 2,000 

 feet thick. It moved northward, and was 

 discharged upon the plains ; some of it evi- 

 dently moved down the caiion through which 

 the Truckee River now flows. 



This glacier was fed by tributaries from 

 the mountains, and these continued to flow 

 after the great mer de glace had ceased to 

 exist. Enormous mounds of debris, glacial 

 moraines, occur between the lake-margin 

 and the mountains, cut with wonderful reg- 

 ularity by water; and toward the south- 

 western portion of the lake occur those 



exquisite lakelets which add to the charm 

 of the region. Of these. Fallen Leaf Lake, 

 Cascade Lake, and Emerald Bay, are of won- 

 derful beauty. The green waters of Emerald 

 Bay contrast with the clear blue waters of 

 Lake Tahoe. Lake Valley, in which Lake 

 Tahoe lies, may not have been wholly scooped 

 out by glacial action. Prof. Le Conte sug- 

 gests that an area of depression may have 

 been formed in the proce?'s of elevation of 

 the mountains, which was enlarged and deep- 

 ened by erosion. 



American Grape-Vines and the Phyllox- 

 era. Four years ago Prof. Riley went to 

 France to study, on the spot, the grape- 

 Phylloxera. Some of the scientific results 

 of this visit as the establishment of the 

 identity of the European insect with that 

 found in our own vineyards, and the Ameri- 

 can origin of the Fhylloxera are known 

 to our readers; but the practical results are 

 highly interesting and important. His ex- 

 perience, here, having taught him that some 

 of our indigenous vines offered greater re- 

 sistance to the insect than the European 

 varieties, and that, with European vines, 

 there was no hope of discovering a rem- 

 edy which would prove practicable and 

 satisfactory on a large scale, and under all 

 conditions, he advised the French grape- 

 growers, as one of the most promising 

 means of restoring the ravaged vineyards, 

 to import American vines, either for their 

 fruit or as stocks for the French varie- 

 ties. Results are fast justifying this ad- 

 vice. The insect continues to broaden 

 the area of its devastations ; and in many 

 sections of Southern France, where but a 

 few years ago the whole country was one 

 great vineyard, the ground is now either en- 

 tirely or partly devoted to other crops, to 

 which it is poorly suited, or the vineyards 

 are rapidly perishing. In spite of the large 

 national reward for a remedy in spite of 

 the well-directed and persistent efforts of 

 the government, and of the Academy of 

 Science, to discover one nothing but sub- 

 mersion, which is practicable to but a lim- 

 ited extent, proves effectual, and by degrees 

 the fact is being acknowledged that all 

 other remedies are futile. The American 

 vines, however, are fast gaining ground, and 

 the people begin to look to them as a means 



