June i8, 1908] 



NA TURE 



161 



temperature than is generally done. By proceeding in this 

 manner some portions can be converted into yellow- 

 coloured brass, and other parts remain pure copper. 



The contrasts between copper and brass are very marked, 



G. 4. — Copijer and brass coal vas;^ inlaid with zinc. 



but softer effects can be obtained with zinc, aluminium, 

 tin, and other metals. Fig. 4 shows such an inlaid copper 

 vase. 



One beauty about this process of inlaying melak whiih 

 differentiates it from other processes 

 is the soft transition which shades the 

 inlaid metal from the surrounding 

 metal. For instance, it will be 

 observed that when inlaying zinc into 

 copper, the zinc is surrounded by a 

 halo of the brass-coloured allov. 



Mr. Cowper-Coles has also another 

 process, which he calls Cowperising, 

 and in which he uses vapour of zinc ; 

 the articles to be coated are not 

 brought into contact with dry or 

 molten zinc, but are placed in a 

 chamber into which zinc vapour is 

 passed. The chamber or drum is 

 slowly rotated inside an outer cylinder 

 in which the metallic zinc is heated by 

 means of a gas or electric furnace. 

 Hydrogen gas is also passed into the 

 apparatus from a tube, and a pilot 

 light is kept burning to make sure 

 that air is not being sucked back. 



The process has been found success- 

 ful for decorating porclnin and 

 metallic surfaces with a brilliant coat- 

 ing of zinc. The remarkable part 

 about the action of zinc powder upon 

 metals is the manner and speed with 

 which it, at temperatures much below 

 its melting point, sinks into and 

 alloys with them. In this, -Sherard- 



ising rather resembles .Sir W. Roberts-Austen's experi- 

 ment in which he placed pieces of gold and lead together, 

 and showed that diffusion took place even at ordinary 

 temperatures ; in his case, however, the diffusion was 



NO. 2016, VOL. 78] 



very slow. But with the Sherardising process the zinc 

 sinks in in a few minutes to an appreciable depth. 

 .Another peculiarity is that the zinc does not require 

 to be pure, but is the commercial dust which is coated 

 with o.xide, and with this zinc dust 1 have found 

 that it is practically impossible to get an electric current 

 to pass through even a centimetre thickness, although 100 

 volts pressure was employed. Cadmium and a few other 

 metals can also be employed, but they are not so satis- 

 factory as zinc. 



It looks as if the zinc has a very distinct vapour 

 pressure even a very long way below its melting point, 

 not to say its boiling point. The zinc vapour being 

 immediately able to alloy with tlie iron or other metal in 

 contact with it, equilibrium is destroyed, and a further 

 portion of the zinc becomes vaporised. F. M. P. 



STUDIES OF SOME AMEiaCAX 

 METEORITES. 



^ 



T 



HE large crater, three-quarters of a mile across and 500 

 feet in depth, near Canyon Diablo, in Arizona, which 

 it is supposed was produced by the impact of an enormous 

 meteorite, has already been described at some length in 

 N.\TURE (igob, vol. l.\.\iv., p. 490J. Since that date the 

 locality has been visited by Dr. George P. Merrill, of the 

 United States National Museum, and. in a paper published 

 in the Smithsonian Miscellaneous Collections (190S, vol. 1, 

 pp. 461-90, with fifteen plates) he gives the results of his 

 observations, and reviews the evidence for and against 

 the meteoric hypothesis. In the hope of finding a large 

 mass of metallic nickel-iron, Messrs. D. M. Barringer and 

 B. C. Tilghman have made a detailed examination of the 

 crater, and have put down a number of bore-holes to the 

 depth of 1 100 feet in its floor. Beneath the surface debris 

 from the sides of the. crater there is a thick bed of lake 

 deposits ; this lies on a crushed and pulverised sandstone 

 containing fused and pumiceous fragments and particles 

 of nickel-iron, while at a depth of about 600 feet the un- 

 disturbed red sandstone of the district was met with. No 

 large mass of meteoric iron was encountered ; and with 

 the exception of four small pieces, the numerous masses of 

 Canyon Diablo meteoric iron have all been found outside 

 the crater. All the evidence undoubtedly points to the 

 crater having been formed by the impact of a meteorite. 

 Prof. O. C. Farrington,' in his " Meteorite Studies, 



Mass produced by joining the two individuals of the Chupaderus inctcuiitt-. a ^'g. 



II.," published in the geological series of the Field 

 .Museum of Natural History (Chicago, 1907), gives a 

 collection of miscellaneous notes respecting nine different 

 meteoritic falls in the North and South .American con- 



