74$ 
Analyses of Books. 
[November, 
The Ocean , a Treatise on Ocean-Currents and Tides and their 
Causes , demonstrating the System of the World. By 
William Leighton Jordan, F.R.G.S. Second edition, 
abridged and revised. London : Longmans, Green, 
and Co. 
The fundamental idea of this work is to be found in the fifth 
chapter, where we have an investigation of vis inertice. As it is 
well known, Newton defined vis inertice as “an innate force of 
matter or power of resisting, by which every body, as much as in 
it lies, endeavours to persevere in its present state, whether it be 
of rest, or of moving uniformly forwards in a right line.” 
(“ Principia, Book I. Definition III.). 
Our author does not accept Newton’s definition. He argues 
“ that any bodies have an innate tendency to move uniformly 
forward in a right line is mere assumption. ... It is said that, 
in the simple case of a ball, thrown in the air and rolled on the 
ground, being set in motion, its vis inertice tends to keep it in 
motion until it is stopped by the resistance of the air or the 
Iridtion of the gronnd against which it runs. This is an error. 
It is not the vis inertice of the ball which tends to keep it in 
motion. It is vis inertice, and vis inertice only, which stops and 
must in time stop the cause of that ball. Vis inertice resists the 
motion of the ball from first to last. ... It thus appears that 
if, in any body whatever, there be not some motive force adting 
continuously to keep it in motion, its own inherent power of vis 
inertice must (even if no other cause arise) in the course of time 
bring it to rest. 
The difference between Newton and Mr. Jordan is easily seen. 
According to the former, vis inertice causes matter to persist in 
its condition, whether of rest or of uniform rectilineal motion. 
According to Mr. Jordan, vis inertice causes matter not only to 
remain at rest, but if set in motion to tend to a return to rest. 
Our author views the tides and the earth’s rotation as the 
main causes of oceanic currents, and of the trade winds. Start- 
ing with the experimental fadt that if a vessel containing water 
is set in motion the water tends to lag behind, he applies this 
principle to the hypothetical cases of a globe entirely covered by 
water, of an ocean surrounded by land, and to the case, as we 
adtually find it, of an ocean whose movements are more or less 
intercepted by continents. 
