394 Scientific Entelligence. [May, 
President.—Sir William Blizard, F.R.S. “ual 
Vice-Presidents.—James Hamilton, M.D.; George Vaux, Esq.; 
John Meyer, M.D.; Lewis Leese, Esq. 
Treasurer. Benjamin Robinson, M.D. 
Secretaries.—John T. Conquest, M.D. F.L.S.; Thomas J. Ar- 
miger, Esq. 
Couancil.— Thomas Addison, M,D.; Thomas Bell, Esq. F.L.S.; 
Henry James Cholmley, M.D. ; Thomas Calloway, Esq.; Wil- 
liam Cooke, Esq. ; George Edwards, Esq.; James Alex. Gor- 
don, M.D.; William Kingdon, Esq.; Benjamin Pierce, M.D.; 
James Parkinson, Esq.; Henry Richard Salmon, Esq.; Fred. 
Tyrrell, Esq. 
The Hunterian Society holds its meetings every alternate 
Wednesday evening throughout the year at No, 10, St. Mary- 
Axe. 
XIX. Observations on the Magnetic Needle. By Col. Beaufoy. 
(To Dr. Thomson.) 
MY DEAR SIR, Bushey Heath, April 1, 1819. 
Having completed two years’ observations on the daily varia- 
tion of the magnetic needle, I have the pleasure to send you a 
table, containing the comparison of monthly observations. As 
every observation was made by myself, and great attention paid, 
I trust they have been conducted with as much accuracy as the 
nature of the subject admitted. It appears by the table that the 
variation increased from the month of April, 1817, until January, 
1819 ; it decreased during the month of February, and increased 
in March the same year; consequently it remains uncertain, if 
the compass be yet arrived at its greatest western variation. By 
taking the mean of the morning differences of the two years’ 
observations, the increase of the ‘variation is 2’ 18”; by taking 
the mean difference between the noon observations, the mcrease 
is 215”; and the mean difference of the evening observations 
gives an augmentation of 2’45”; mean of the whole 2’ 25”. 
Table II. contains the mean difference of the two years’ obser- 
vations, between the morning and noon and the noon and even- 
ing obséryations, whence it appears that the greatest daily 
variation takes place in the month of April, and the least im the 
month of December, the former being 11’ 48”, and the latter 
4’ 07”, and that the differences in April and August are nearly 
the same. 
As the variation of the needle appears to be a subject of 
general interest at present, it is my intention to continue my 
observations, which I trust you will as usual permit to be 
inserted in the Annals of Philosophy. 
I remain, my dear Sir, yours very sincerely, 
Mark BeEavroy. 
