76 Electricity. — Queries. 
pings are heard, exactly like (though not so loud as) the dis- 
charge of the Leyden jar; this continues frequently as long as it 
is heid in the hand; sometimes indeed after a short interval it 
ceases, but the crackling may be again produced by warming it. 
Now, as we know this substance is one of the most perfect 
negative electrics, are we to infer that the bare holding it in the 
hand is sufficient to excite it, and to produce the same effects 
as are obtained from a glass tube, or other electric, by friction ? 
It is clear that the noise is occasioned by the comuiunication of 
a certain portion of its electricity to the hand, as it is never 
heard: when approached by ancther electric body ;—a piece of 
metal warmed, which is an equally good conductor with the hand, 
also produces the saine sound. T have no doubt but that in 
the dark this noise would be accompanied by a scintillation si- 
milar to that produced by the approach of a non-electric body 
to-an excited glass tube. As it is generally believed that hold- 
ing a picce of ‘sulphur i in the hand is a cure for the cramp (2 and 
{ am viven to understand by a friend who has tried it, that it 
has that property) ; are we to attribute its efficacy in this in- 
stance, to the power it possesses of imparting a certain quantity 
of electricity to the hand, which, by immediately acting on the 
complaint, at once alleviates anc removes it ? 
Any information on this curious subject will be gladly re- 
ceived by 
Your constant reader, 
Jan, 22, 1816. Jer: 
QUERIES. 
To Mr. Tilloch. s 
Sir,—I shall consider it a favour, if you will publish in your 
valuable Magazine the following queries and observations: they: 
may lead to some information, which will be as acceptable to 
many of your readers, as to your constant student, 
Vert INVESTIGATOR. 
The principle of bevelled wheels was, | believe, first published 
by De La Hire in the ixth volume of Mémoires de l’ Académ. 
Paris, 1666 to 1699. But I would gladly be informed where 
and when they were first put in action ?. 
What is the date, and by whom were governors or lift-tenters: 
first applied to coru-mills driven by wind? and where was the 
first governor applied to the steam-engine ? 
The Swedes contend with us for the priority of invention of _ 
the thrashing-machine. Can you inform me, whether they 
have any just ground for such a claim? If they have not, I 
imagine that Mr. Sterling of Perthshire was the inventor about 
1758. Has 
