VOL. Llll.} PHILOSOPHICAL TRANSACTIONS. 705 



XXII f. Observations 071 Electricity j and on a Thunder-storm. By Mr, Tor- 

 hern Bergman, F. R. S. Acad. Reg. Upsal. Soc. From the Latin, p. 97. 



With regard to the electrical experiments with island crystal, given by Mr- 

 Delaval, in the Philos. Trans., vol. 52, p. 355, Mr. B. here states, that after 

 often repeating those experiments, he always found a contrary result. Thus, 

 he exposed various pieces of this crystal to 12 degrees of cold of the Swedish 

 thermometer, filled with quicksilver, being the degrees of cold below the 

 freezing point of water, of which there are 100 between the freezing and boil- 

 ing points of water. He then rubbed it after the space of some hours, but 

 without producing any except a very small degree of electricity. Next day he 

 repeated the experiment with a greater degree of cold, but with still less success. 

 He next heated a small piece, hoping thus to eradicate its whole force ; but un- 

 expectedly he found its electric virtue not at all destroyed, but much increased. 

 This being found to be the case with all the specimens he could collect, he 

 suspects there are different kinds of this crystal, endued with such different pro- 

 perties. And indeed Mr. Delaval had said as much in his paper. ^ 



The thunder-storm happened at Upsal, Aug. 24, 176O; but there is nothing 

 very remarkable in the account. 



XXI f^. Remarks on Swallows on the Rhine : in a Letter from Mr. Achard, in 

 Privy-Garden, to Mr. Peter Collinson, F.R.S. p. 101. 



In the latter end of March I took my passage down the Rhine to Rotterdam : 

 a little below Basil the south bank of the river was very high and steep, of a 

 sandy soil, 60 or 80 feet above the water. I was surprized at seeing near the 

 top of the cliff, some boys, tied with ropes, hanging down, and searching, as 

 we were informed, the holes in the cliff for swallows, or martins, which took 

 refuge in them, and lodged there all the winter, until warm weather, and then 

 they came abroad again. 



The boys being let down by their comrades to the holes, put in a long rammer 

 with a screw at the end, as is used to unload guns, and, twisting it about 

 drew out the birds. For a trifle I procured some of them. When I first had 

 them they seemed stiff and lifeless. I put one in my bosom, between my skin 

 and shirt, and laid another on a board, the sun shining full and warm upon it. 

 That in my bosom revived in about \ of an hour ; feeling it move, I took it 

 out to look at it, and saw it stretch itself on my hand, but perceiving it not 

 sufHciently come to itself, I put it in again : in about another quarter, feeling 

 it flutter pretty briskly ^ I took it out and admired it. Being now perfectly re- 

 covered, before I was aware, it took its flight, but the covering of the boat pre- 

 vented me from seeing where it went : the bird on the board, though exposed to 



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