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PRESIDENTIAL ADDRESS-—PRIESTLEY. a 
terms of circulaz motion; an idea from which even Kepler 
found it hard to break away and which hindered the 
development of Astronomy ; but it is not a great time since 
Biology and Geology were handicapped by a universal 
belief in the literal truth of the early chapters of Genesis, 
and at the present day Einstein is assailed with arguments 
based on the assumption of the objective reality of the 
ther. 
The reaction against the barren metaphysical science 
of the Middle Ages set in towards the end of the sixteenth 
century and gradually gathered strength. The state of 
affairs in the early eighteenth century is well shewn up 
in the editor’s preface to the second edition of Newton’s 
Principia, published in 1713. In this preface Cotes, 
Plumian Professor of Astronomy and Experimental Phil- 
osophy in the University of Cambridge, summarizes the 
methods of the old and new schools of thought, and refers 
in addition to a third school occupying an intermediate 
position. That the new views had not found universal 
acceptance is evident from the fact that he considers it 
advisable to devote considerable space to a refutation of 
the Cartesian Vortex Hypothesis. In view of the light 
thrown on the scientific thought of Newton’s day by this 
preface, I ask your attention to a somewhat free translation 
of some extracts. 
“Students of Physics can be divided into three classes. 
For there are some who attribute specific and oceult 
qualities to the several species of things from whence 
they derive, I know not by what process of reasoning, the 
behaviour of individual bodies. Herein is found the whole 
doctrine of the schoolmen, derived from Aristotle and the 
Peripateties; they assert that each individual effect arises 
from the special natures of bodies; the origin of those 
natures they do not tell and hence they teach us nothing. 
Since all is in the names of things, not in the things them- 
selves, we can allow that they have found a certain 
philosophical language, but they have given us no 
Philosophy. 
‘Others, again, have hoped to gain credit for better 
discretion by rejecting this useless accumulation of words. 
They maintain that there is a universal homogeneous matter 
and that all variety of types which is observable in bodies 
arises from the simplest and easily understood relationships 
