528 Intelligence and Miscellaneous Articles. 



way. Other experiments follow, in which the lead was maintained 

 at 200°, and at various lower temperatures down to that of the 

 laboratory. The following are the results : — 



Diffusivity of gold in fluid lead at 550 .... 3-19 



solid 



55 



55 



55 



55 



55 



55 



55 



55 



251 .. 



. . 0-03 



200 .. 



. . 0-007 



165 .. 



. . 0-004 



100 .. 



. . 0-00002 



The experiments at the ordinary temperature are still in pro- 

 gress, but there is evidence that slow diffusion of gold in lead 

 occurs at the ordinary temperature. The author points out that if 

 clean surfaces of lead and gold are held together in vacuo at a 

 temperature of only 40° for four days, they will unite firmly, and 

 can only be separated by the application of a load equal to one- 

 third of the breaking strain of lead itself. 



The author thinks it will be considered remarkable that gold 

 placed at the bottom of a cylinder of lead, 70 millims. long (which 

 is to all appearance solid), will have diffused to the top in notable 

 quantities at the end of three days. He points out that at 100° 

 the diffusivity of gold in solid lead can readily be measured, though 

 its diffusivity is only 1/100,000 of that in fluid lead at a tempera- 

 ture of 500°. He also states that experiments which are still in 

 progress show that the diffusivity of solid gold in solid silver, or 

 copper, at 800° is of the same order as that of gold in solid lead 

 at 100°. 



He concludes by warmly thanking Mr. A. Stansfield, B.Sc.,who 

 assisted him in all but the earlier portion of the work, and by 

 expressing the hope that the experiments described in the paper 

 will show that the diffusion can readily be measured in solid 

 metals, and that they will carry one step further the work of 

 Graham. — Proceedings of the Royal Society, February 20, 1896, 

 being an abstract of the Bakerian Lecture. 



RONTGEN RAYS NOT PRESENT IN SUNLIGHT. BY M. CAREY LEA. 



If Prof. Rontgen's views as to the nature of the #-rays are cor- 

 rect, it would seem that they ought to be found amongst the 

 many forms of radiant energy received from the sun, and various 

 observers have thought that they so found them. Some experi- 

 ments, the most important of which will be here briefly stated, do 

 not seem to support this opinion. 



1. A very sensitive dry plate (S. 27) was placed between the 

 leaves of a book so that 100 leaves and the red paper cover should 

 be between the sensitive film and the sunlight. The book was 

 then packed in a box-frame to exclude all light from the sides. A 

 large and thick lead star was then fastened on the outside of the 

 book and the arrangement was exposed to exceptionally bright 

 sunshine from 11 a.m. to sunset, March 7. The plate when put 



