such powers of mind must be due to certain subtle influences at work through heredity in society; and the commingling of innumerable and widely-different ancestral germs, co-operating with favorable conditions for their manifestation, must suffice to explain the observed facts. Dr. Wallace offers a very different explanation, and holds that the facts "clearly point to the existence in man of something which he has not derived from his animal progenitors-something which we may best refer to as being of a spiritual essence or nature, capable of progressive development under favorable conditions."

On the other hand, Mr. Galton, although leaning strongly against the doctrine of the transmission of acquired qualities, has, in his "Hereditary Genius" and other works, ably shown from concrete examples that high qualities of mind tend to run in particular families, and has done much to disprove the popular notion, relied on by Weismann, that they are spasmodic products of the Zeitgeist. In the same line with Galton, M. Alphonse de Candolle, himself a notable example of "hereditary genius," has collected an additional mass of facts in support of the view that talents tend to persist in certain families or lines of descent. There are, it is true, many apparent exceptions to this rule, but most of them could probably be explained if all the facts were known. It is not to be supposed that there will be in every case a series of direct descendants, all displaying the same mental powers in a progressively increasing degree. Aside from the now well-understood law of atavism, which often makes long breaks in such series, a multitude of other influences tend to modify and distort the effects, and finally wholly to destroy them. The most important of these influences is, of course, the commingling of different strains in the two parents. The single fact that, as a rule, the sexes prefer their opposites would rather make us wonder that any one class of mental qualities can be perpetuated through two generations. And it is the recognition of this fact that has led some to propose an abandonment of the rule of personal choice, and to recommend the selection by parents and guardians of similar natures, instead of opposite ones, to be the parents of the race. But such persons forget that in the union of opposites nothing is lost of the qualities of either,

but only the tendency to extremes is checked. And, assuming the qualities thus neutralized to be worthy, many maintain that this leavening of the whole mass of society is more to be desired than the exaggeration of a few of even the noblest attributes.

Weismann and his followers do not generally deny that the faculties above enumerated have increased, and greatly increased. The chief explanation seems to be that this is effected by the fortunate union of varied ancestral qualities in the developing germ. Prof. E. Ray Lankester argues that they may have arisen more or less suddenly, as in the case of what are called "sports," and that this may be brought about by external influences acting abruptly and spasmodically upon the reproductive elements of the parents. He denies that the nature of the effect can have any qualitative relation to the cause, and compares this relation to that which the shaking of a kaleidoscope sustains to the change produced in the images exhibited. To the average mind this certainly seems far less reasonable than to suppose that the prolonged exercises and intense activity of a particular faculty has the effect, in some unexplained way, of producing in the parental germ a corresponding alteration which is capable of perpetuating itself in the offspring, and thus of transmitting to descendants the increment acquired by the parent through cultivation and personal exertion.

But aside entirely from all abstruse theories as to how heredity takes place, we have at least the following general facts, which can best be explained by the theory of the transmission of acquired qualities: Correlated with the general process of cephalization, which is admitted to be due to other causes, a large number of highly derivative and greatly specialized mental attributes that offer no advantage in the struggle for existence have made their appearance in man. These have arisen, so far as we know, only under the protection of such social institutions as are calculated to exempt a portion of the race, for longer or shorter periods, from the necessity of devoting its energies exclusively to the maintenance of physical existence; that is to say, they are the products of leisure, and represent the surplus mental energy insured by civilization. With the satisfaction of physical wants these intellectual, esthetic, and ethical wants have arisen, grown

powerful, and been attended with intense emulation. This has led to the incessant and vigorous exercise of these derivative faculties. Although not advantageous in the biological sense, these faculties have, nevertheless, been strengthened and increased pari passu with their exercise. They are most highly developed in those persons who have most strenuously cultivated them, as witness the ethical cast of the Hebrew mind, the talent for sculpture among the Italians, and the musical genius of the Germans. The faculties themselves are clearly hereditary and, notwithstanding parental crossing and other distributive influences, tend perceptibly to persist for a longer or shorter period in particular families.

The whole point at issue is whether there is a causal relation between the cultivation of these faculties and their development; in other words, whether the increment gained by their exercise is transmitted to posterity. Professor Weismann and most of his followers, constituting what is now generally known as the school of Neo-Darwinians, deny such transmission. If they are right, education has no value for the future of mankind, and its benefits are confined exclusively to the generation receiving it. So far as the inculcation of knowledge is concerned, this has always been admitted to be the case, and the fact that each new individual must begin at the beginning and acquire all knowledge over again for himself is sufficiently discouraging, and has often been deplored. But the belief, though vague, has been somewhat general that a part at least of what is gained in the direction of developing and strengthening the faculties of the mind, through their life-long exercise in special fields, is permanently preserved to the race by hereditary transmission to posterity of the acquired increment. We have seen that all the facts of history and of personal observation sustain this comforting popular belief, and until the doctors of science shall cease to differ on this point and shall reduce the laws of heredity to a degree of exactness which shall amount to something more like a demonstration than the current speculations, it may perhaps be as well to continue for a time to hug the delusion.

LESTER F. WARD.

CHEMISTRY TO-DAY AND ITS PROBLEMS.

IF we compare the chemistry of the present day with that existing in the earlier half of the century, we certainly see no epoch-making, far-reaching discovery such as that which has marked the sister science, biology. There is nothing which warrants us in speaking of the "new" or of the "old" chemistry. Nevertheless we have witnessed a most important advance. Our science is gaining a more complete organic and internal cohesion, and is entering into closer federal relations with the other sciences, giving and receiving fresh light. Chemistry, in conjunction with physics, furnishes astronomy with a new and most powerful method of research, and with a new body of facts and generalizations. But to these results we have no occasion to refer, as they have been ably explained by Professor C. A. Young.*

At the same time, chemistry is deriving new light from the very opposite direction. Not many years ago few persons, if any, surmised that certain microscopic living beings-microbia, or micro-organisms could be powerful agents of combination. and decomposition, not merely in living plants and animals, and not alone in dead organic matter, but even in the mineral kingdom. Some time ago the researches of Schloesing and Muntz, of Marcagno, of P. F. Frankland, and of others showed that the decomposition of dead organisms into their components depends mainly on the action of microbia which break up blood, flesh, leaves, and even wood, into carbonic acid and ammonia. Living organisms further convert the ammonia into nitric acid, which, if potash is present, forms saltpetre. By a due selection of different ferments-all of them living organisms-we can produce, in a solution of sugar or a decoction of malt, alcoholic liquors having the actual aroma and flavor of the choicest wines. More remarkable still, it is now proved that the green rust on antique bronzes is a product of microscopic plant life.

*The FORUM, September, 1890.

The interfusion-not confusion-of chemistry and physics is being rapidly developed, and is constantly proving more and more fruitful. Just as the miner is apt to find the amplest booty where different rock formations meet; just as the flora and the fauna are richest where land and water adjoin each other; so also the border land of chemistry and physics forms the happy hunting ground of the experimentalist-a truth which I would strongly urge upon every student.

We were told formerly that bodies cannot act upon each other chemically except after they have been dissolved. Yet even gravitation, the least versatile form of energy, can, when it acts as pressure, compel certain solid bodies to enter into mutual combination even at ordinary temperatures. W. Spring, a Belgian chemist, by submitting sulphur and copper, in the form of fine powder, to an enormous pressure, has been able to combine the two chemically, forming a copper sulphide; and, in an analogous manner, it is possible to form the sulphides of other metals which have a powerful affinity for sulphur. This experiment has a most important bearing upon the formation of minerals in that part of nature's laboratory which we call the interior of the earth. Of the processes in play in that laboratory we know very little, as our main evidences are merely rocks raised by upheavals and matter ejected by volcanoes.

An important result of the joint action of low temperature and intense pressure is the liquefaction, and even the solidification, of gases. Faraday formerly experimented in this direction with no little success, but certain gases bade defiance to the resources at his disposal and remained in the gaseous condition. Consequently in old text books we used to read of "condensible" and of "permanent" gases. But of late the question has been re-opened with improved methods and more powerful appliances. Pictet, Cailletet, and Wroblewski have been so successful that the class of "permanent gases" has disappeared. It has been asked what would be the condition of any substance, or of matter in general, if it could be exposed to the temperature of absolute zero supposed to exist in the depths of space. Such a body, so far as we can judge from approximate experiments, need retain none of the properties of matter save inertia and