335 
level, attached to the base, serves to indicate any change 
which may occur in the level of the instrument. The magnet 
is of course covered with a box, to protect it from the agita- 
tion of the air; and the apparatus is furnished with several 
minor pieces, which are employed in the various adjustments. 
In addition to these instruments, which are those in con- 
stant use, the Observatory is furnished with an inclination 
instrument and a pair of needles, made by Gambey; a transit 
instrument and large theodolite, used chiefly in determining 
the absolute declination; a transit clock and a chronometer ; 
and a complete set of meteorological instruments. 
Mr. Lloyd closed his communication with a brief account 
of the important undertaking in which her Majesty’s Govern- 
ment had recently engaged, for the purpose of advancing the 
knowledge of Terrestrial Magnetism—an undertaking which 
he characterized as the vastest in its design, as it might also 
be expected to be the most fruitful in its results, of any which 
the British, or any other government, had ever engaged in, 
in behalf of science. 
The Secretary read the following communications from 
George James Knox, Esq., giving an account of his further 
researches on Fluorine: 
1. On the Insulation of Fluorine. 
“In a paper on the Insulation of Fluorine which the Rev. 
Thomas Knox and I had the honor of presenting to the 
Royal Irish Academy in the year 1837, and which was after- 
wards published in their Transactions, (vol. xviii. p. 127,) we 
proved that we had obtained fluorine in an insulated state, 
by shewing its action upon bismuth, palladium, and gold; 
but being unable, from our mode of experimenting, to deter- 
mine what the nature of fluorine at ordinary temperatures 
might be, i.e. whether it be a solid, a liquid, or a gas, we 
suggested that such information might be obtained from the 
2a2 
