t 88o.] On Water and Air. 5 11 
degree, and it was soon found, after the experiment of Torri- 
celli, that the height of the column of mercury varied from day 
to day, and varied sometimes very rapidly indeed ; and that 
proved to people in those days that the piessure of the 
atmosphere was by no means a constant thing. Sometimes 
the atmosphere was lighter, and sometimes it was heavier 
than at other times ; and Boyle observed for five weeks the 
oscillations of the height of this barometric column, and in 
that way saw clearly the variations in the pressure of the 
atmosphere. It is these pressures, or at least these vai a- 
tions of pressure, that now enable us more or less to predict 
the advent of certain kinds of weather'. Here in London, 
for instance, when the north-east wind blows, you would 
usually find a high barometer as it is called, — that is to say, 
the atmosphere, being chilled by the north-east wind, is 
denser or heavier, and it is able to support a higher mercuiial 
column than when, for instance, the west wind blows, which 
comes to us charged with light aqueous vapour from the 
Atlantic, warmed more or less, and the consequence is that 
this lighter air is not able to sustain the same height of the 
mercurial column. Well, this was one of the early obser- 
vations made by Robert Boyle, and he made various other 
observations with his air-pump. He made observations 
upon the influence of air upon respiration, and we know a 
great deal about these matters now; but it was of infinite 
importance to break ground in. this region — to get some 
experimental grasp of this region which .was not at all 
known before. The proper aCtion of the air upon animals 
was not known, and he put snails and caterpillars, and mice 
and rats, and I think even a dog, under the receiver, of his 
air-pump, to observe the effeCt of withdrawing the air from 
those animals. He produced very wonderful results, which 
caused him to lift his heart in gratitude to the Creator for 
making the air so essential to animal life and enjoyment.. 
I dwell upon Boyle particularly, because he was a.scien- 
tific character and a philosopher worthy of all imitation by 
the younger scientific philosopher. He was a man who not 
only possessed the highest intellectual culture of his age, 
and who made important discoveries, but he united to this 
power of a scientific man those characters and qualities 
that we essentially ascribe to the human heart the quali- 
ties of tenderness, and courage, and courtesy. And let me 
say to you, my young friends, once for all, that scientific 
knowledge unless backed up by those other qualities leaves 
you not rounded men, but only lopsided men. 
Well, this I have thought it my duty to say with regard 
VOL. II. (THIRD SERIES). 2 N 
