A CATALOGUE OF OBSERVATIONS OF LUMINOUS METEORS. 33 



ofF If by 1 inch in size and ^g oz. in weight ; this was carefully polished for 

 the purpose of examination when exposed to heat. But what a surprise I 

 After the colour of the principal mass had passed through the various shades 

 of straw-yellow, brownish-yellow, violet, and blue, there remained groups 

 of triangles of straw-colour parallel lines, the blue and violet intervals I to 

 •I line wide, the straw-yellow lines ^ to ^ — a splendid phenomenon. This was 

 the first observation, and the figures were called " Widmanstatten's figures," 

 in honour of the discoverer. The method of etching by acids was introduced 

 after this discovery. 



2. Leitform — In a paper on a typical form of meteorites, presented at 

 the meeting of the Imperial Academy of Vienna, on April 19th, I860, by 

 Prof. Haidinger, he suggests some new and interesting ideas. The paper is 

 accompanied by two plates of the appearances of meteoric stones from Stan- 

 nern and Gross-Dwina, which are complete in themselves, and may be con- 

 sidered as individuals of their kind, which at the same time show distinctly 

 one of the periods through which they have passed. 



In viewing meteorites there must be a starting-point from some funda- 

 mental considerations proved by the phenomena themselves, in order to arrive 

 at an understanding of their forms and conditions. These are, 1st, the stone 

 leaving the extra-terrestrial space as a solid ; 2nd, its velocity being greater 

 on entering the earth's atmosphere ; 3rd, it is retarded by the resistance of 

 the air ; 4th, the " fireball " (or luminous envelope of the meteor) formed by 

 the compression of the air and the rotation of the stone resulting therefrom ; 

 5th, the termination of the first part of the path is marked by a detonation, 

 the so-called explosion, the vacuum inside of the fireball being suddenly filled 

 by the surrounding air. 



The Stannern stone seems to have passed through the air with its rounded 

 side first, and shows over its surface effects resulting from a uniform action of 

 the atmosphere upon it whilst the crust was in a viscous state. The lustrous 

 crust is surrounded by a protruding gibbosity ; the stone had sharp edges 

 which in the foremost direction of the meteorite were melted off and blown 

 towards the back part. The time of the passage through the air generally 

 lasts only a few seconds. The rising temperature producing the crust belongs 

 to this period, since the stone came from the planetary space wiih a tempera- 

 ture of 100° C. below freezing-point. Some meteors get heated very rapidly ; 

 masses of iron will sometimes get red-hot whilst one composed of some other 

 substance will be quite cold inside ; and as soon as the detonation takes place, 

 and the fireball disappears, the inside and outside temperatures of the me- 

 teorites are soon counterbalanced and the crust rapidly cools, especially at a 

 height where the temperature is very low. 



The stone of Gross-Dwina, which in its general character is allied to those 

 of Timochin, Zebrak, and Eichstadt, shows a great dissimilarity on its two 

 principal planes, one being smooth, and the other rough. The form is that 

 of a fragment altered only on its surface. Characteristic of this meteorite is 

 a ridge which passes over the " head " of it; and corresponding with it there 

 was one passing over the back part of it. The roundish spots where a 

 melting off has commenced have a striking resemblance to the impressions of 

 figures in dough ; they are generally to be found on the side best protected 

 during its passage. 



3. St. Denis- Westrem. — At a meeting of the Imperial Academy of Vienna 



on October 4th, 1860, Director Haidinger gave an account of this meteorite. 



The fall took place vvithout detonation, and only a slight noise was heard 



similar to the rattling of carriages, on June 7th, 1855, 7| p.m., near the town 



of St. Denis-Westrera, 2\ miles from Ghent. 



1861. D 



