57 
hammering ; upon annealing in a charcoal fire, the mean 
density of five out of the ten pieces was 8*896, showing a gain 
of 0*018 upon the hammered pieces, and a loss of 0*002 
upon the original. A third series of experiments upon the 
change of density in a bar of copper by successive hammerings 
showed a loss of density from 8*885 to 8*867. 
The Author considered there was a connexion between these 
phenomena and the heat disengaged in the hammering of the 
copper ; he conceived it possible that the expanded state of 
the copper while heated by hammering was retained, and that 
the effect of annealing might be to allow the molecules or 
particles to recover the state in which they were in before 
being disturbed by the heat produced in hammering. 
PHYSICAL AND MATHEMATICAL SECTION. 
February 28 th, 1861. 
Mr. G. V. Vernon, F.R.A.S., read a Paper, “ On the 
Irregular Oscillations of the Barometer at Manchester.” 
This Paper is an addition to one upon the same subject 
brought before the Society by Mr. Baxendell, F.R.A.S. 
The tables appended to it give the total amount and 
number of the barometer oscillations at eight a.m., for each 
month from 1849 to 1860, inclusive ; the mean daily 
amount ; the monthly fall of rain, and its difference from the 
average of twelve years, and Dr. JDal ton’s forty-seven years’ 
average. For the month of August, the Author was indebted 
to the kindness of Mr. John Curtis, in supplying him with baro- 
meter observations, which were deficient in his own register. 
The maximum amount of oscillation takes place in January, 
and the minimum in July, to which may be added a second 
maximum appearing to take place in October. The mean 
total amount of oscillation for the year is 61410 inches, and 
