558 



SCIENCE. 



[N. S. Vol. VII. No. 173. 



cality myself, but the prints were obtained 

 by me from tbe original photographer in 

 Moab, when on^ a somewhat hurried return 

 from a mine examination in the Blue Moun- 

 tains to the south. The dimensions of the 

 bridge, as estimated by the photographer, 

 are about 500 feet in span and about 150 

 feet in height. A comparison of the bridge 

 with figures shown in the original photo- 

 graph in the right-hand corner and with 

 the tree growth near by indicates that these 

 dimensions are quite possible. 



The bridge is, in all probability, a mon- 

 strous product of wind erosion. The rock 

 appears to be one of the friable Mesozoic 

 sandstones which are widely exposed in this 

 region. Other examples of wind action, 

 such as is illustrated in figure 2, were seen 



by me while travelling through the country, 

 so located that no other cause could be as- 

 signed. Strong and prolonged winds are 

 frequent here, as any one who has sojourned 

 in that country can testify to his miserJ^ 

 The sands carried by these winds are 

 whirled about in the depressions of the 

 rocks, and excavate wind pot-holes in the 

 friable sandstones with great rapidity. A 

 wall or slab of such rock is by degrees en- 

 tirely penetrated, giving rise to the so-called 

 window rocks which are frequently seen in 

 isolated buttes high above the surrounding 

 level. Our natural bridge, I conclude, is 

 simply an extreme or abnormal enlarge- 



ment of such a 'window.' Possibly some 

 water channel may have assisted in the 

 process, but the view does not indicate this, 

 but shows the bridge to be high above the 

 main water course. The dimensions of the 

 bridge, or rather the shape of the space 

 covered by it, are also against this idea, as 

 the ordinary channel cut by a stream 

 through rock is deep and narrow. 



Arthur Winslow. 

 Kansas City, Mo., 



February 25, 1898. 



FIFTH ANNUAL RECEPTION AND EXHIBITION 

 OF THE NEW YORK ACADEMY 

 OF SCIENCES. 

 The fifth annual reception and exhibition 

 of the New York Academy of Sciences, of 

 which notice has already been made in 

 Science, was held in the American Museum 

 of Natural History, April 13lh and 14th, and 

 proved to be the most satisfactory and suc- 

 cessful of all receptions thus far given by 

 the Academj'. The number of exhibits was 

 not as great as heretofore, but was arranged 

 to show the progress of the last year more 

 carefully than had been the custom pre- 

 viously. Hence the exhibit, as a whole, 

 was worthy of detailed attention in every 

 department and received such attention 

 from the several thousand people who were 

 present during the two evenings and one 

 afternoon on which the reception was held. 

 Beside the exhibit" of progress in some fif- 

 teen departments of science, of which more 

 particular mention will follow, the pro- 

 gram included an address on the second 

 evening by Professor George E. Hale, of 

 the Yerkes Observatory, on the ' Functions 

 of Large Telescopes,' which will appear in 

 a later number of this Journal. Mr. C. 

 E.Tripler gave several demonstrations of 

 the properties of liquid air to an astonished 

 and appreciative audience. Indeed, liquid 

 air was the exhibit of the reception con- 

 cerning which the most questions were 

 asked. 



