Correspondence 



467 



vegetable structure becomes obvious. These corallines are abundant 

 on the English coast, but not very conspicuous. They often grow 

 almost after the habit of a lichen on the surface of a stone, or they 

 may be found in rock-pools, constituting short tufts. 



The Archeopteryx. — " It cannot be said that this ancient 

 extinct bird goes far towards connecting birds with reptiles, but in 

 the possession of separate claw-bearing fingers, a long bony tail and 

 teeth, in the apparent want of a beak, it does come nearer to lizard- 

 like reptiles than does any other known bird." — Ray Lankester, 

 239. 



The atmosphere is forty-five miles in height. If it were through- 

 out of the same density as at sea-level it would be only about a ninth 

 of that height (or five miles). Air is 810 times lighter than water and 

 11,000 lighter than mercury. Pressure, 15 lbs. on the square inch. 



In a recent number of Nature we notice an advertisement offering 

 £5 17s. 6d. per ounce for old platinum crucibles, &c. 



The same weight of this metal was worth about £1 15s. in the year 

 1880. 



The present high price of platinum is due to its extensive use 

 during late years in the platinotype photographic process, which has 

 created so great a demand for it that all the known sources of supply 

 threaten shortly to become exhausted. This costly metal is found 

 in Borneo, some of the western states of America, Canada, Australia, 

 and a few other places. The chief locality, however, is the Ural 

 Mountains in Russia. It almost invariably occurs in association 

 with various other rare metals, one of which, viz., osmium, is the 

 heaviest of all known substances, platinum being only slightly lighter. 



Crucibles, spatulas, &c, made of platinum, are much used in 

 chemical and physical laboratories, the metal being especially suited 

 for such purposes on account of its high melting point, and also by 

 reason of the properties which it possesses of remaining unoxidised 

 by the atmosphere, at all temperatures, and being unacted upon by 

 acids. 



The editors of the Naturalist say of the Selby Museum : u We 

 are sorry to see from a report of an address recently delivered at 

 Selby by Mr. Hutchinson, that this Museum is not appreciated as it 

 ought to be." This statement is an error, for nothing of the kind was 

 suggested. The Museum is exceedingly well appreciated, and so 

 well visited that its charge of a penny admission almost, if not quite, 

 pays the cost of maintenance. What was said referred solely to the 

 local collection, and the regret expressed was that classes on special 



