98 Prof. W. N. Hartley and Mr. H. Eamage. The Mineral 



the result that he collected a similar powder. The snow gathered in 

 the latitude of 80° N. in an expedition to Spitsbergen, and that 

 collected from floating ice in the Arctic regions and on the glaciers of 

 Greenland, leaves, after it has melted, a greyish residue, which consists 

 largely of diatomacese, but mixed with these organisms there were 

 also particles of a carbonaceous dust of considerable size, which on 

 analysis were found to contain metallic iron, cobalt, and nickel, also 

 silicon, carbon, and phosphorus. The origin of this mineral matter 

 was at first doubtful. Two of its constituents, cobalt and nickel, were 

 believed to be of very uncommon occurrence in terrestrial matter, 

 while on the other hand they are elements invariably associated with 

 the metallic iron of meteorites, the nickel being more particularly in 

 large proportion. If we suppose that this dust is discharged from the 

 mouth of a distant volcano, or that it may be sand carried up by a 

 whirlwind, we have yet to explain the peculiarities in its composition 

 which render it similar to that of meteorites. 



Nordenskjold arrived at the conclusion that it was meteoric matter 

 which had descended upon the earth in a shower similar to that which 

 occurred near Upsala. By the facts which he had collected it appears 

 to have been proved that cosmic dust is falling imperceptibly and 

 continually. It seems that this view is either generally not accepted, 

 or that the facts are not commonly known. 



Very little is really known about the composition of atmospheric- 

 dust, notwithstanding that searching investigations were made by 

 Pasteur and Angus Smith, aided by the microscope, and later by Liveing 

 and Dewar by the aid of the spectroscope. 



Professor O'Eeilly, M.R.I.A., supplied us with small quantities of a 

 material concerning the nature of which he was desirous of obtaining 

 information. On inspection it appeared to be of an unusual character 

 for mere town dust, and accordingly we submitted it to a spectro- 

 graphs analysis, and determined the principal metallic elements which 

 enter into its composition. The following specimens in particular have 

 been examined with care : — 



(I.) Solid matter which fell in or with hail in a hail-storm on 

 Wednesday, April 14, 1897, and was collected by Professor O'Reilly 

 at a window facing the large open space of Stephen's Green, at the 

 Royal College of Science, Dublin. It contained iron, sodium, lead, 

 copper, silver, calcium, potassium, nickel, manganese a trace ; gallium 

 and cobalt gave doubtful indications. 



(II.) Solid matter from hail and sleet collected by Professor O'Reilly 

 from a window-sill of the Royal College of Science, Dublin, during a 

 very heavy shower, from 2.30 till 3 o'clock, in the afternoon of March 

 28, 1896. 



Total weight of the dust 0T018 gramme, of which 0'08 gramme 

 was burnt in the oxy hydrogen flame. The colour of the dust was steel 



