20 
The quantity of water from rain and melted snow, was 5:1 
inches. 
The mean humidity was 64.25°. On the 17th and 18th 
complete saturation (100°) prevailed, while the minimum was 
reached on the 25th, when it was only 27.6, giving a range of 
72.4 for the month. 
The maximum of the barometer was 80.182 inches, on the 
5th, and the minimum, 29.884 inches on the 12th, a range of 
.748 inch. The mean for the month was 29.779 inches. 
The casual phenomena observed, were lightning on the 
1st, thunder showers on the 2d, 5th, and 6th, one lunar halo, 
and one lunar corona. 
May 12th, 1873. Chemical Section. 
President Newberry in the chair.. Thirty-two persons present. 
Dr. H. ENDEMANN read the following paper : 
The Air we Breathe. 
During the month of February, 1873, I commenced an in- 
vestigation, which from want of time, could not be so 
thoroughly treated as the importance of the subject requires. 
This is an investigation regarding the composition of air in 
school-rooms, factories, theatres, halls, tenements, and cellar 
lodgings. 
The impurities generally found in the air of inhabited 
places, are carbonic acid, vapors of various organic sub- 
stances, and dust. 
The latter is seldom found in much larger quantity inside 
of structures than outside, with the exception of certain 
places, where peculiar manufactures may contribute largely to 
its quantity. In the manufactories of curled horse-hair, for 
instance, the room in which the horse-hair is spun is filled 
with a dense cloud of dust, which, when collected and 
examined, appears to be a mixture of inorganic substances 
with those of organic origin. Of the latter, fine, sharp-edged 
pieces of horse-hair form evidently the most dangerous part, 
inasmuch as they irritate the mucous membranes of the air- 
passages, and therefore become the cause of the various affec- 
