130 Annals of the Philosophical Club 



himself and his guest, M. Cahours, 1 showed ammonia (NH 8 ) 

 and phosphuretted hydrogen (PH 3 ) to have a great analogy. 

 As in compounds of the former, each equivalent of hydrogen 

 may be replaced by ethyl, methyl, and amyl, so, in the 

 latter, the same can be done, thus forming new and highly 

 basic substances in every way corresponding with the 

 hydrogen compounds. 



M. Cahours, in reply to an enquiry from Admiral Smyth 

 about the cost of manufacturing aluminium, specimens of 

 which had attracted so much notice at the Paris Exhibition, 

 said that some totally different method of manufacture must 

 be devised, before it could be produced cheaply, so that at 

 present it was regarded as a curiosity, which had only a 

 theoretical interest. 



Colonel Sabine gave an account 2 of a remarkable tornado 

 which had occurred on April soth, 1852, near New Harmony, 

 in Indiana, U.S. The breadth of the whirling air-column 

 appears to have been about a mile, and at nine or ten miles 

 on either side the air was calm enough to allow of ordinary 

 agricultural work, but in the track of the tornado, trees, 

 many of them 15 feet in circumference, were overthrown, 

 frequently being twisted half round before this happened. 

 Its axis moved at the rate of about 60 miles an hour, first 

 N. 30 E. for 50 miles, and then a little N. of E. for 200 miles 

 further, the change of direction corresponding with an angle 

 in the Ohio valley, to which its course was roughly parallel. 

 The sky was described by persons in the neighbourhood 

 as a cloud, with vivid blue, green and red light on its 

 lower part. At 3 p.m., in a place four miles on one side 

 of the axis, the thermometer stood at 80 and the barometer 

 at 29-09 inches. At 4 p.m. the first flash of lightning 

 occurred, which was followed by a heavy, driving hailstorm ; 

 the stones sometimes measuring 8 inches in circumference 

 and weighing four ounces. At that time the thermometer 



1 Probably Professor A. A. T. Cahours, a distinguished French chemist, 

 elected Professor of Chemistry in the cole Polytechnique at Paris, who was 

 born Oct. 2nd, 1813, and died March iyth, 1891. 



8 It had been published in Smithsonian Contributions, vol. vii. article 2. 



