Works of Herbert Spencer pulished by D. Appicion & Co.

THE CONDITIONS ESSENTIAL TO HUMAN HAPPINESS SPECIFIED, AND THE FIRST OF THEM DEVELOPED.

In one Volume. Large 12mo.

All these works are rich in materials for forming intelligent opinions, even where we are unable to agree with those put forth by the author. Much may be learned from them in departments in which our common Educational system is very deficient. The active citizen may derive from them accurate systematized information concerning his highest duties to society, and the principles on which they are based. He may gain alearer notions of the value and bearing of evidence, and be better able to distinguish between facts and inferences. He may find common things suggestive of wiser thought -nay, we will venture to say of truer emotion-than before. By giving us fuller realisations of liberty and justice his writings will tend to increase our self-reliance in the great emergency of civilization to which we have been summoned.-Atlantic Monthly

THE CORRELATION AND CONSERVATION

OF

FORCES.

▲ SERIES OF EXPOSITIONS BY GROVE, MAYER, HELMHOLTZ, FARADAY, LIEBIG, AND CARPENTER.

WITH

AN INTRODUCTION.

BY E. L. YOUMANS

The work embraces:

I. THE CORRELATION OF PHYSICAL FORCES. Br W. R. GROVE. (The complete werk.)

II. CELESTIAL DYNAMICS. BY DR. J. R. MAYER.

III. THE INTERACTION OF FORCES.

HOLTZ.

BY PROF. HELM

IV. THE CONNECTION AND EQUIVALENCE OF FORCES. BY PROF. LIEBIG.

V.-ON THE CONSERVATION OF FORCE. Br DR FARADAY.

VI. ON THE CORRELATION OF PHYSICAL AND VI

TAL FORCES. BY DR. CARPENTER.