66 Royal Society : — 



eddy, the eddy itself being caused by the meeting of very extensive 

 bodies of air, moving in nearly, but not exactly opposite directions, 

 one of which gradually overpowers, or combines with the other, after 

 the rotation. 



On the polar half of the cyclone, continually supplied from that 

 side, the visible effect is a drying up and clearing of the air, with a 

 rising barometer and falling thermometer ; while on the equatorial 

 side, overpowering quantities of warm moist air — rushing from 

 comparatively inexhaustible tropical supplies — push towards the 

 north-east as long as their impetus lasts (however originated), and 

 are successively chilled, dried, and intermingled with the always 

 resisting, though at first recoiling, polar current. After such 

 struggles these two currents unite in a varying intermediate state 

 and direction, one or other prevailing gradually. 



Very plain and practical conclusions are deducible from these 

 considerations : — 



One, and the most important, is that in a gale which seems likely 

 to be near the central part of a storm, that should be (of course) 

 avoided by a ship which has sea room : a seaman, facing the wind, 

 knows that the centre is on his right hand in the northern hemisphere, 

 on his left in the southern ; he therefore is informed how to steer. 



Another valuable result is that telegraphic communication can 

 give notice of a storm's approach, to places then some hundred miles 

 distant, and not otherwise forewarned. 



Jan. 12, 1860. — Sir Benjamin C. Brodie, Bart., Pres., in the Chair. 



The following communications were read : — 



" Notes of Researches on the Poly ammonias.'' — No. VII. On 

 the Diatomic Ammonias. By A. W. Hofmann, LL.D., F.R.S. 



In continuing my inquiries into the nature of the organic bases, 

 I was led in the commencement of the year 1858 to repeat some 

 experiments on the action of dibromide of ethylene upon ammonia, 

 which M. Cloez* had published in 1853. The repetition of these ex- 

 periments compelled me to contest not only the formulae of M. Cloez, 

 but also the general interpretation which he had given to his results. 



I have not hesitated to communicate my conclusions to the Royal 

 Society-)*. 



M. Cloez J shortly afterwards discussed my observations, and 

 pointed out the arguments which induced him to maintain his 

 formulae and his interpretations. 



I have not replied to these remarks. M. Cloez having stated in 

 the same note that he was still engaged with his experiments and 

 that his inquiry was nearly completed, I discontinued my experi- 

 ments on the action of dibromide of ethylene upon ammonia, fully 

 persuaded that the chemist, to whom we are indebted for the first 

 observation of this reaction, in continuing his experiments would 

 arrive at the same results which I had myself obtained. 



In discontinuing the discussion with M. Cloez, I was not freed 

 from the obligation of proving the general thesis of my note, viz. 

 * L'Institut, 1853, p. 213. f Phil. Mag. vol. xvi. p. 309. 



\ Comptes Rendus, xlvi. p. 255. 



