VOL. XXVI.j PHILOSOPHICAL TRANSACTIONS. 3Q5 



were not reflected: and this I have often found to be very serviceable in mea- 

 suring distances: for example, standing on the banks of the Thames, opposite 

 to Woolwich, the echo of a monosyllable was reflected from the opposite 

 houses in 6 half seconds of time; hence I concluded the breadth of the river 

 in that place, from one side to the other, to be 17 12 English feet, or upwards 

 of 4^ of a mile; for as 9.25 half seconds : to 5280 (the number of feet in a 

 mile) :: 6 half seconds : to 3424.8 feet, the half of which is 1712.4 feet. 



6, Lastly, the height of thunder-clouds, as also the distance of the thunder 

 and lightning itself, may by this means be easily known. 



Account of the strange Ejects of Thunder and Lightning. By Samuel Moly^ 

 neux, Esq. S. Phil. Soc. Dublin. N°313, p. 36. 



Mrs. Close gave Mr. Molyneux the following account of the effects of the 

 thunder and lightning, on her house at New Forge, in the county of Down, 

 in Ireland, on Aug. C), 1707: she observed, that the whole day was close, hot, 

 and sultry, with little or no wind stirring, till towards the evening; that there 

 was a small breeze with some mizzling rain, which lasted about an hour ; that 

 as the air darkened after sun- set, she saw several faint flashes of lightning, and 

 heard some thunder claps, as at a distance; that between 10 and 11 o'clock 

 both were very violent and terrible, and so increased, and came on more fre- 

 quently until a little before 12 o'clock; that one flash of lightning and clap of 

 thunder came both at the same time, louder and more dreadful than all the 

 rest, which, as she thought, shook and inflamed the whole house; and being 

 sensible at that instant of a violent strong sulphureous smell in her chamber, 

 and feeling a thick gross dust falling on her hands and face as she lay in bed, 

 she concluded that part of her house was thrown down by the thunder, or set 

 on fire by the lightning; that arising in this fright, she called up her family, 

 and candles being lighted, she found her bed-chamber, and the kitchen 

 beneath it, full of smoke and dust; and the looking-glass in her chamber 

 was broken. 



The next day she found that part of the cornish of the chimney, which 

 stood without that gabel-end of the house, where her chamber was, had been 

 struck off; that part of the coping of the splay of the gabel-end itself was 

 broken down, and 12 or 16 of the shingles on the adjoining roof were raised 

 or ruffled, but none shattered or carried away; that part of the ceiling in her 

 chamber, beneath those shingles, was forced down, and part of the plaster and 

 pinning stones of the adjoining wall, was also broken off and loosened, the 

 whole breach being 16 or 20 inches broad: that at this place there was left on 

 the wall a smutted scar or trace, as if blacked by the smoke of a candle, which 



3 £ 2 



