A Class-Book of Chemistry; in which the Latest Facts and Principles of the Science are explained and applied to the Arts of Life and the Phenomena of Nature.  A New Edition, entirely rewritten.  By EDWARD L. YOUMANS, M.D.  New York:  D. Appleton & Co.

Though Science has been often vaguely supposed to be something generally distinct from ordinary knowledge, yet the slightest consideration will suffice to show us that this is not the case.  Scientific knowledge is only a highly developed form of the common information of ordinary minds.  The specific attribute by which it is distinguished from the latter is quantitative prevision.  Mere prevision is not peculiar to science.  When the school-boy throws a stone into the air, he can predict its fall as certainly as the astronomer can predict the recurrence of an eclipse; but his prevision, though certain, is rude and indefinite:  though he can foretell the kind of effect which will follow the given mechanical impulse, yet the quantity of effect—­the height to which the stone will ascend, and the rapidity with which it will fall—­is something utterly beyond his ken.  The servant-girl has no need of chemistry to teach her, that, when the match is applied, the fire will burn and smoke ascend the chimney; but she is far from being able to predict the proportional weights of oxygen and carbon which will unite, the volume of the gases which are to be given off, or the intensity of the radiation which is to warm the room:  her prevision is qualitative, not quantitative, in its character.  But when Galileo discovers the increment of the velocity of falling bodies, and when Dalton and De Morveau discover the exact proportions in which chemical union takes place, it is evident that knowledge has advanced from a rudely qualitative to an accurately quantitative stage; and it does not admit of dispute that the progress of science is thus a progress from the indefinite to the definite.

From the point of view here taken it would appear that during the present century no science has made such rapid and unprecedented strides as Chemistry; and its progress becomes all the more striking, when we consider the state of the science previous to the French Revolution.  For centuries nothing had been done in it whatever.  Besides the commonest previsions of every-day life, the ancients knew scarcely anything either of chemistry or physics, except that amber possessed attractive properties.  The discovery of the strong acids by the Arabs Giafar and Rhazes, and of phosphorus by Bechil, are almost the only landmarks in the history of the science, until the discovery of oxygen and the destruction of the phlogistic theory by Priestley and Lavoisier, together with the introduction of the balance and the thermometer into the laboratory, rendered quantitative experiments possible.  Since then its progress has been unexampled.  The law of definite proportions, not long since disputed or unwillingly accepted, has been proved to hold even