122 



THE POPULAR SCIENCE MONTHLY. 



Workshop Appliances ; including Descrip- 

 tions of the Gauging and Measuring 

 Instruments, the Hand Cutting-tools, 

 Lathes, Drilling, Planing, and other "Ma- 

 chine-tools used by Engineers. By C. 

 P. B. Shelley, Civil Engineer. 209 Il- 

 lustrations, 312 pages. Price, $1.50. 

 D. Appleton & Co. 



This is a hand-book of tools and their 

 uses, compendious in form, and copiously 

 illustrated, which will be of great value to 

 young artisans and mechanics, whether 

 working in wood or metal. There is no end 

 to machines for reshaping the materials of 

 Nature, and inventors are constantly adding 

 to them ; but the fundamental tools for pro- 

 ducing mechanical effects, with their re- 

 sources of variation, fall into a few classes, 

 and their modes of action are capable of 

 explanation within a narrow space. It is 

 the variation and recombination of com- 

 paratively a few implements that are con- 

 stantly coming before us in the form of com- 

 plex and obscurely - acting contrivances. 

 Two objects are to be gained by the use of 

 tools : 1. The production of given mechani- 

 cal effects ; and, 2. Accuracy in the pro- 

 cesses. Both of these objects are now at- 

 tained by mechanics with a remarkable de- 

 gree of perfection. Mr. Shelley describes 

 these in clear and simple language, which, 

 with his excellent illustrations, makes the 

 subject quite intelligible to ordinary readers. 

 Besides its value as a practical hand-book 

 to the working mechanic, this little volume 

 will have great interest for those who wish 

 to understand how the wonders of modern 

 construction are executed. 



MISCELLANY. 



Yosemite Valley of Glacial Origin.— In 



the summer of 1872, Prof. Joseph Le Conte, 

 of the University of California, with several 

 students of the institution, visited the Yo- 

 semite and the mountains contiguous, and 

 carefully examined the results of the gla- 

 cial action which were everywhere appar- 

 ent. His conclusion's were stated in an able 

 paper, published in the American Journal 

 of Science for May. The Yosemite Valley, 

 he thinks, was once filled to the brim with 

 a great glacier. In this he differs from 

 Prof. "Whitney, who in his guide-book ex- 



i presses the opinion that there is no evi- 

 dence that such a glacier existed. 



Prof. Le Conte observes that glaciated 

 forms are unmistakably observable at many 

 points on the walls of the valley, and in 

 some places even to the brim. In the con- 

 tour of the walls of the valley, their round- 

 ed form, where the rock is hard, standing 

 unbroken and without debris at the base, 

 he finds proofs of glacial erosion. On the 

 north side of the valley, every projecting 

 shoulder is thus rounded, and in some cases 

 the smoothness is so complete, even at a 

 considerable height, that the rocks glisten 

 in the sunshine. Where the rocks are soft, 

 and on the southern side of the valley, which 

 is in shadow, frost and other agencies have 

 done their work of disintegration. The sur- 

 faces are broken, and the debris lies at the 

 base. 



The bed-rock of the valley is covered 

 with mounds of bowlders and sand, which 

 are terminal moraines of glaciers, and by 

 stratified lake-deposits, the lakes having been 

 formed by the glacial mounds obstructing 

 the flow of waters. 



But it was from the higher elevations 

 that the wonderful features of the glacial 

 erosion were most distinctly observed. 

 " From the edge of the rim of Little Yose- 

 mite," says the author, " we had a magnifi- 

 cent bird's-eye view of the wonderful dome- 

 like form of nearly all the prominent points 

 about this valley, and their striking resem- 

 blance to glaciated forms cannot be over- 

 looked. The whole surface of the country 

 is rnoutonne on a huge scale. If so, then 

 the greater domes about the Yosemite have 

 been formed in a similar manner. If so, 

 then the whole surface of this region, with 

 its greater and smaller domes, has been 

 moulded beneath a universal ice -sheet, 

 which moved on with steady current, care- 

 less of domes." 



This great ice-sheet preceded the sep- 

 arate glaciers which completed the erosion 

 of the valleys of which Yosemite is one, 

 and the scattered snow-fields which were 

 discovered by Mr. Muir, of the expedition, 

 are feeble remains of the old glaciers. In 

 the opinion of Prof. Whitney, the Yosemite 

 was formed by a sudden engulfment of a 

 portion of the sierras, but Prof. Le Conte 

 observes that Yosemite is not unique in 



