402 Scientific Intelligence. [May, 
This appears to me extremely curious; as the cause (which I 
should presume was electrical), one should think, would possess the 
same power ten minutes before as ten minutes after one o'clock ; 
and what is still more curious is, that, having produced the effect 
related, it should almost instantly cease to act, as the piece of metal 
soon becomes stationary, and must be removed from the glass before 
it will again vibrate. 
Very little attention appears necessary to perform this experi- 
ment ; although it will not always succeed. A sixpence, or piece 
of metal rather heavier, will in general be found to answer. 
It will give me great pleasure to see your opinion and theory, or 
that of any of your numerous readers, respecting this curious phe- 
nomenon, in a future number of your Annals. 
I am, Sir, your obedient servant, 
Barnet, April 2, 1817. Tuos, S. Booru. 
— 
The phenomenon observed by Mr. Booth will naturally bring to 
the recollection of electricians the experiments of Mr. Stephen 
Gray of the revolution of small balls held in the hand by a string 
round large ones, and always in a direction corresponding with the 
motion of the sun. He bequeathed these experiments at his death 
as a kind of legacy to his electrical friends. ‘The subject was soon 
after investigated with all the requisite care by Mr. Wheeler, who 
succeeded in demonstrating that the revolutions in question were not 
owing to any electrical property whatever, but to the voluntary action 
of the hand that held the string. Mr. Gray, though an acute man, 
was not aware that he exerted any such voluntary power; and it 
was by no means an easy task for Mr. Wheeler to ascertain this to 
be the true cause. I have no doubt that the motion of the sixpence 
in the experiment of Mr. Booth is owing to the voluntary action of 
his finger and thumb ; and that he will be able to satisfy himself 
that this is the case by varying his trials, and by resolving beforehand 
that the sixpence shall strike some hour different from that which 
has struck last.—T. 
VII. Further Improvement in Brooks’s Blow-pipe. 
(To Dr. Thomson.) 
DEAR SIR, 
I, in a former number, suggested an idea for the improvement 0 
Mr. Brooks’s blow-pipe. If you think proper to give insertion to 
the following in your Journal, you will greatly oblige me. 
Instead of having the apparatus made with two gasometers, I beg 
Jeave to suggest the propriety of having 
them formed in this manner: the hydrogen, 
being confined in two reservoirs, will in all 
probability tend in a great measure to pre- 
vent explosion. I trust you will make a trial of the propriety of 
this idea. The only objection lam aware of that can be brought 
Hyd. | Hyd, | Oxy. 
