72 
magnetic force of the needles, as deduced from observations 
of the previous year; this may not be precise, and may 
slightly change the number. The two needles gave respec- 
tively : 
Bar. Cylinder. Diff. 
.9576 . 9607 .0031 
“Taking your result for Dublin and London, and Captain 
Sabine’s for London and Paris, I deduce for the ratio of 
Edinburgh and Paris, (the latter being unity) 0.8406 ,—which 
is nearly identical with the direct comparison made by Pro- 
fessor Forbes. It disagrees very materially with the result 
of Captain Hall, by whom Edinburgh and London were first 
compared ; but as the locality of his observations was shown 
by Mr. Dunlop to have rendered them inaccurate, they can- 
not be said to make against these determinations. I have 
not yet had an opportunity to see how far Mr. Dunlop’s 
correction would make the three sets coincide. 
** My determinations give: 
Philadelphia, . . . 1.0000 
ubina,? ..  ~.. OSS00 
Edinburgh, .)".2 > >. 0.7957 
But, of course, the correction for the loss of magnetism 
by the needle, if not exact, would affect these results more 
than that for the two last named places.” 
DONATIONS. 
Flora Batava, No. 109. By H. C. Van Hall. Presented 
by the Author. 
A Copy of the Ordnance Survey of the County of Meath, 
in 55 sheets. Presented by Lieutenant-Colonel Colby. 
On the Arenarius of Archimedes. By Stephen Peter 
Rigaud, M.A., Savilian Professor of Astronomy, Oxford. 
Presented by the Author. 
Mean Heights of the Barometer and Thermometer, with the 
Fall of Rain, at the Observatory, Oxford, during each month 
of the years 1828 to 1856. Presented by the same. 
