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Scientific Intelligence. 
each with a piece of soft iron. By these rules, magnets of extra- 
ordinary power may be made. 
ACOUSTICS. 
6. Velocity of Sound. — The velocity of sound in the atmos- 
phere has been recently measured with great care by a com- 
mittee of the Members of the Institute of France, consisting of 
MM. Prony, Bouvard, Mathieu, and Arago. The result of 
their observations was, that at the temperature of -f- 10° of the 
centigrade thermometer, the velocity of sound in a second is 
173.01 toises, or 337.2 metres, = 110.6 English feet, and 4 
inches at the temperature of 50° of Fahrenheit. The academi- 
cians, in the year 1738, had obtained 173.84 toises at the same 
temperature. — Biblioth. Universelle , Sept. 1822, p. 27. 
7. On Sounds excited in Hydrogen Gas. — When we insert- 
ed in No. XIII. a notice * of Mr Leslie’s experiments on the 
sounds excited in hydrogen gas, we were not aware that similar 
experiments had been made, so early as 1812, by Messrs Kerby 
and Merrick, till it was pointed out to us by an esteemed corre- 
spondent. “ I have not,” he remarks, fiC the Transactions of the 
Philosophical Society of Cambridge, and I cannot therefore tell 
what Mr Leslie’s experiments may be ; but if they only go to 
shew that hydrogen is a bad conductor of sound (and this is 
what I collect from your account in the Philosophical Journal), 
the fact has been established long ago. You will find it in 
Nicholson’s Journal , vol. 33. p. 168, among other experiments 
of the same kind on different gases, made by Messrs Kerby and 
Merrick in 1812 *f\” These very curious experiments, with ad- 
ditional calculations, have been republished by Mr Farey sen . 
in the article Gases in the Edinburgh Encyclopedia, vol. x. 
p. 121. Our correspondent will observe, that we have given in 
No. XIII. all the facts in Mr Leslie’s paper, which occupies 
only a few lines more than a page in the Cambridge Memoirs. 
• The word Rarefaction in that notice was twice misprinted, from the types 
being transposed, and falling out. 
•j* M. C-hladni of Wirtemberg had determined very long ago, that both hydro- 
gen and azote give a note considerably lower than what we should infer from cal- 
culation. 
