811 



past, that the certain result of all meteoric coruscations and irides- 

 cences in the sky, is a fall of rain, snow or hail, — on this general prin- 

 ciple, that the condensation of the crystalline particles of floating 

 vapours which ensues upon electrical action, must be followed by pre- 

 cipitation ; and these coruscations and iridescences are both the 

 reflected evidences of such condensation of crystalline matter, and 

 therefore the harbingers of such precipitation. It is the case with 

 solar and lunar rainbows, falling stars, mock-suns, halos, lightning, 

 aurora, and that undefined pearly lustre which sometimes appears 

 in the neighbourhood of the sun. 



"Accordingly, on the following morning, Saturday the 18th, I 

 found the barometer had sunk considerably, and the wind had veered 

 round from north-west to south-west, against the course of the sun, 

 both in general, and especially when united, the forerunners of rain. 

 Accordingly at 2 o'clock p.m. a smart shower came on in Northamp- 

 ton, but was of short duration. At 9 p.m. a heavier shower was ex- 

 perienced at Brix worth ; and in the course of the night, but I cannot 

 say at what hour, I was awakened to a still heavier shower ; but the 

 quantity of rain that had fallen did not seem to have afl'ected the 

 ground much on the following morning, and therefore I conclude 

 that it was not great. 



" Sunday the 19th was fine and bright ; the wind went up to the 

 westward, and the barometer rose rapidly — a general indication of 

 an early change. Towards morning of Monday the 20th, another 

 shower fell, and the wind went back to the south-west with a falling 

 barometer. In such cases I generally find that rain ensues about 

 midday, or at least when the wind and sun meet in the south-west. 

 But on this occasion it continued blowing strong all the day, and 

 for some time in the night with increased violence. But at last the 

 wind fell, and was succeeded for awhile by heavy rain, thus verify- 

 ing my anticipations on this particular occasion, and the general 

 theory which I have discussed." 



March 29, 184.9. 



GEORGE RENNIE, Esq., Treasurer, Vice-President, in the Chair. 

 The following papers were read : — 



1. " Examination of the Proximate Principles of some of the Li- 

 chens." — Part II. By John Stenhouse, Esq., F.R.S. 



Gyropliora pustulata. 

 The author states that this lichen, which is the " Tripe de Roche" 

 of the Canadian hunters, has been long employed by the manufac- 

 turers of archil, though the quantity of colouring matter contained 

 in it is by no means considerable, being little more than a twelfth 

 of that in the Roccella 3Iontagnei. The GyropJwra pitstidata, on 

 which the author operated, was brought from Norway, where it is 



