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suspended by a single filament of silk ; its shorter arm being 
connected with the first lever by means of a small hook 
attached to the fibre d. The whole is enclosed in a stout 
copper box, into which light is admitted through a lens e , 
cemented into an orifice immediately under the object glass 
of the microscope f. 
The microscope magnifies about 300 linear, and has a 
micrometer in its eyepiece, with divisions corresponding to 
2 cfW of an inch. One division corresponds to a deflection of 
the needle of 4J", and as a tenth of a division can be very 
readily observed, the instrument measures deflections to 
within half a second. So rapid is the action, that on apply- 
ing a small magnetic force the index takes up its new position 
steadily in two seconds of time. Besides being a damper to 
the motion of the needle, the copper box, by its conducting 
power, equalizes the temperature rapidly, so that the indica- 
tions are not to any considerable extent disturbed by currents 
of air. The success of the present instrument encourages 
the hope that very much greater delicacy may be obtained 
by a further multiplication of the motion and the use of a 
more powerful microscope. Dr. Joule stated that he had 
observed an extensive magnetic disturbance the preceding 
evening, the index being driven entirely out of the field of 
view. 
The President said that three meteorological instruments 
of true originality and of unprecedented delicacy had been 
described to this Society by the inventor Dr. Joule. For 
common observation the instruments were too refined, but in 
some fields of enquiry they seemed the only hopeful guides. 
Manchester has not yet a Meteorological Observatory, 
although the proposal has often been made to establish one. 
Private spirit, as in the instance of Mr. Vernon and others, 
has made the necessity less felt than before. But there is now 
an opportunity of beginning one with entirely new apparatus 
of Manchester origin, which would probably very much alter 
