452 . Intelligence and Miscellaneous Articles. 



During preliminary experiments made in Colorado Springs, ifc 

 was found that a sheet of aluminium would allow certain solar 

 rays to pass through. These were not Eontgen rays, for the 

 reason that black paper placed between the aluminium and the 

 photographic plate seemed to cast as deep a shadow as did a strip 

 of iron. A different mode of exposing the plate was necessary 

 and a plan similar to Lea's was finally adopted. 



The first 100 leaves of an unbound book were turned over, and a 

 rectangular trough of the dimensions of the photographic plate 

 (7*5 by 13 cm.) cut into the next 55 pages. Seven pages above 

 this trough, thin metallic plates, from 5 to 20 mm. wide, were 

 placed between two leaves, and held in position by gumming the 

 two leaves together. Care was taken to let the mucilage dry before 

 shutting the book. After the photographic plate (Seed, 23) was 

 placed in the trough, the book was closed, wrapped in black 

 tissue-paper, then in paraffine paper, and finally put into a tin 

 box. 



The box was prepared as follows : — Its lid was placed externally 

 over its bottom and a rectangular window, 7*5 by 13*5 cm., cut 

 through them both. Thereupon a sheet of aluminium, 13 by 

 23 cm., and -29 mm. thick, was placed between the lid and the 

 bottom, so as to screen the window. The wide margin of the 

 aluminium, lying between the sheets of tin, was united to them 

 above and below by thin layers of bees'-wax. Externally the 

 edges of the rectangular window were covered with sealing-wax, 

 to which a thick layer of paint was finally applied. A new lid 

 was provided for the open side of the box and both lids were 

 soldered on. Prepared in this manner, the box could be left 

 exposed to all kinds of weather without danger that moisture 

 would reach the photographic plate. To touch the plate, rays had 

 to penetrate the sheet of aluminium, a few layers of paraffine and 

 black paper, and 100 pages of the book. Eontgen rays of intensity 

 ordinarily met with in the laboratory penetrate at once very much 

 greater thicknesses of these materials. 



Through the kindness of Mr. P. Blackmer and Mr. D. Eupp, of 

 Colorado Springs, the box was taken to the summit of Pike's Peak 

 (elevation 14,147 ft.) and fastened by wires upon a roof sloping 

 southward. The box was left in that position from June 27 to 

 August 10. When subjected to the usual process of development, 

 the plate failed to show any action of rays and presented a uniform 

 surface, without traces of shadows from the metallic strips. 

 Another plate, similarly exposed from July 7th to August 28th in 

 Eosamont Park, near Pike's Peak, at an altitude of 9200 ft., gave 

 the same result. 



Thus even in high altitudes no evidence of the presence of 

 Eontgen rays in solar radiation was obtained. — Am. Journ. Set. 

 [4] ii. 1896, p. 289. 



