VOL. LXXIII.] PHILOSOPHICAL TRANSACTIONS. 380 



feet ; but the part of the wire on which the lightning passed was about 15 feet. 

 Near the crank iron that was directly over the bolt were two wires, which passed 

 through the wainscot to a single one belonging to an alarm. The lightning 

 passed these two wires, without damaging them ; but the single one was partly 

 dispersed into smoke, blackening all the wainscot near it ; also a great deal was 

 melted into globules, which were found by using a magnet. This was the first 

 instance that Mr. N. had ever met with of wire being contracted or shortened by 

 the effect of lightning, though he had not the least doubt, but that it is always 

 the case ; and that is the reason that we find them mostly broke where the light- 

 ning has passed, if it does not melt them. 



To know whether the lightning had anywise altered the property of the iron 

 by melting it into globules, Mr. Cavendish tried them with different acids, and 

 found that they scarcely showed any signs of effervescence even when heated 

 over the fire. He next tried some iron filings, which he put to some of the 

 same acid ; these not only caused an effervescence, but were entirely dissolved. 

 He also tried the pieces of steel struck off by striking a light, which being sepa- 

 rated by a magnet from the pieces of flint effervesced with the same acids, and 

 dissolved almost entirely, only half a grain being left out of 18, and these con- 

 sisted chiefly of those parts that were melted in globules. 



XV. An Account of Ambergris. By Dr. Schwediaiver. p. 226. 



Ambergris, or Grey Amber, is a solid, opaque, inflammable substance, of a 

 white grey, sometimes of a blackish colour, which melted or inflamed yields a 

 peculiar smell, agreeable to most persons, but disagreeable to others. It is a 

 hard brittle substance, yet not so hard as to admit a polish ; nor has it like suc- 

 cinum, a polished appearance or transparency. On scraping it with a knife into 

 powder, part of it adheres to the cold steel like wax ; as it does likewise to the 

 teeth when masticated ; it yields also the impression of the nail ; it has no pecu- 

 liar but rather an earthy taste when chewed. It has in its natural state a peculiar 

 strong smell. The older it grows the more it seems to become agreeable. This 

 smell is rendered more sensible by rubbing it with the fingers, or by burning or 

 melting it. 



It melts in a moderate degree of heat into a blackish thick oil, and then 

 smokes, scums, and flies by degrees entirely off, without leaving any coal be- 

 hind ; as it does likewise when put upon any heated metal, leaving only a black 

 spot on it : when the metal is red-hot, it melts and inflames instantaneously, 

 smokes strongly, and flies speedily off", without leaving the least mark behind. 

 When brought near a burning candle it catches fire immediately, and burns 

 with a clear bright flame till it is consumed. A red-hot needle easily penetrates 

 through its substance, a blackish oil then exudes, but no part of it seems to ad- 



