Physics. 117 
Pursuing the argument further, a south pole and a north pole were 
caused to act simultaneously upon each end of the bismuth bar ; sup- 
posing one end of the latter to be repelled by a south pole, then, on the 
assumption of diamagnetic polarity, the same end would be attracted 
by a north pole ; and permitting both poles to act upon it simultane- 
ously from opposite sides, we may anticipate that the force tending to 
turn the bar will be greater than if only a single pole were used. TT 
test this conclusion, four electro-magnetic cores were made use of ; the 
two poles to the right of the bismuth bar were of the same name while 
the two to the left of the bismuth bar were of an opposite quality ; with 
this arrangement the mechanical action upon the bar was greatly aug- 
mented, and the te oe anticipation completely verified. 
The bar employed in these experiments is unusually large, but it 
does not mark the oration limit of success. All the results obta 
with this bar were obtained with another solid cylinder of bismuth 14 
inches long and 1 inch in diameter. e norrespoeiem experiments 
_. were made with bars of iron, and it was always found that the ar- 
. rangement of forces which caused the attraction of es of the par- 
¥ amagnetic bar caused the repulsion of the ends of t lamagnetic one 3 
__ while the disposition which caused the repulsion of the ends of the par- 
amagnetic bar produced, in the most manifest manner, the atéraction 
of the ends of the diamagnetic one és 
of | polarity, the only difference e 
paratively intense action of LS wi , aint In the case of a magnetic 
Pi Si 
duced in favor of the polarity of the former body that cannot. be 
matched. by proofs of equal value in every respect of the polarity of 
the latter. 
The objections that have heen and possibly may be used against di- 
amagnetic polarity, are next. considered, and some observations are 
ade on the constitution of the magnetic field. The relation of our 
of di 
7a 
to Ampére’s hypothesis of molecular currents is stated ; and in conclu- 
sion, the author dwells briefly upon those points of diamagnetic action 
wherein ane views of M. Matteucci differ from his own. 
— Bui = Biapeersens as and Remarks on the Measurement of Heights 
by a Boiling Point of Water; by Professor J. D. Forbes, (Edinb. 
N. Phil. J., [2], i, 174.)—This paper is in continuation of one printed 
in Sis xv. of the Edinburgh Royal Society’s Transactions. The object 
Of itis to test the correctnes of the method of observation and of cal- 
_ Culating the results, then proposed, and to. compare with those of 
: > Baa recent authors, particularly of M. Regnault of Paris, and of Dr. 
_ Joseph 1D. Hooker. 
The author finds the results of his subsequent — in 1846 j in 
the ee up to heights considerably above 10,000 fe et, to agree well 
with those previously published, made in 1842. They combine if 
tat the rate of 1° for 543 
feet of ascent (in na standard “mea grt here at 32° of temperature), which 
» differs only 6 feet (in defect) from his previous determination. The 
“ soa deviation of’ the individoal results: from the formula is only +), 
a degree -hoog saan regard to sign). 
ae 
