to favor atmospheric oxidation? One of our laboratories here has lately furnished most excellent specimens of this unwelcome intruder, which appear to countenance this latter view. Certainly the hydraulic arrangements of the fungus are well calculated to distribute more water than is needed for its own growth and yet allow a free access of air to the dampened support.

It is possible that biologists at present tend towards extremes in referring so many things as they do to the presence of fungi, which may be the consequence rather than the cause of certain conditions. We should always remember that a problem is far from being solved when we have simply worked out the value of y in terms of the still unknown, and perhaps unknowable x.

It may be pertinent to inquire whether chemistry tends, as many assume that ail physical science now tends, to materialism. I believe no true science tends that way: it is rather the lack of really liberal cultivation that causes such dimness of vision. Surely materialism is no more prevalent now than it was among the ancient Athenians, who had no physical science. We hear much said of the learning and culture of that polished people,-and some of their modern imitators; just as though æsthetics were the only science, and floriculture the only culture!

Doubtless heredity influences personal belief, and the blood of those seventeenth century colonizers still flows in human veins; blood that is thicker than vapid, all attenuating water. But there is much in the training of the chemist to foster a wholesome skepticism and a just intolerance; intolerance of human pride and human dicta; skepticism of the airy theories of pseudo-science. We would by all means welcome free thought; but let it not be the reproduction of other men's opinions; let it not be mere ciphering with algebraic symbols; let it not be ridicule and confident assertion, the glittering weapons of fools; let it be thought and not the spurious semblance of thought. There is a higher standard than ranting declaimers go by. «' Η αλήθεια ἐλευθέρωσε pas." "Ye shall know the truth, and the truth shall make you free."

In chemical practice, the constant appeal to sensible tests and to the precision of the balance checks reliance on hasty assumptions. The stern rule that the sum of the parts must equal the whole, that percentages must count up one hundred, is rigidly en

forced and the discipline is severe but strengthening. The chemist soon learns that exact truthfulness in others and rigid honesty in himself lie at the very foundation of science and real knowledge, and he cannot help looking on laxity in experiment or statement as the unpardonable sin.

Again, the history of chemistry gives little encouragement to conservatism, for perhaps no other subject is so well calculated to impress one with the idea that theories are but the changeable dress of science. "Is not the life more than meat, and the body than raiment." The phlogistic, dualistic, caloric, electrochemical, atomic, nucleus, radical, mechanical, catalytic, and biological theories have all had their uses for a time, they have all aided the progress of science, but in the chemistry of to-day we find only well trimmed shreds of most of them. The review of the enthusiastic but unstable past shows how often men have remained satisfied with explanations which were not reasons. We all wonder what will have become of the atomic theory itself, when the centennial of its promulgation comes round, twenty-seven years hence.

But when we rise above the reactions of brute matter and the play of insensate forces, and are insensibly led on to look into vegetative life, irritability, sensation, perception, thought, the transmission of thought, the self-analysis of thought, and the prime origin of thought, all theories, actual or possible, fail to satisfy. It requires something more than lenses and chemical changes of the retina to see. A noise may ring the tympanum and not be heard. We cannot trace the connection between phosphorus and sparkling wit. Physical science can explain only the tools of thought and cannot explain all there is of them. There is no peculiarity in the matter of the printed page. Its supposed atomic motions give no clew to its marvellous power. As we turn the leaves of the oldest scripture in existence, to the eye alone there is only paper and carbon; yet the alphabetic symbols convey something which is not of them, but beneath, beyond, and above them. Through them we see a grand mirror of human trial. To the ear there is no sound, yet this æonian telephone brings down to us the voice of Zophar the Naamathite uttering the interrogative negation, "Canst thou by searching find out God?" and we hear the yearning cry of Job, "O that I knew where I might find him." Then by "the true Light which lighteth every

man that cometh into the world," we perceive that the revelation of Him as something more than the vague mainspring of creation, as a personal being who still lives and cares for every one of us, comes not by induction, not by syllogistic reasoning, not by algebraic analysis, not by synthetic philosophy, not in acts of terror, not in works of power. It comes in the still, small voice which he who will may hear.

PAPERS READ.

LAWS GOVERNING THE DECOMPOSITION OF EQUIVALENT SOLUTIONS OF IODIDES UNDER THE INFLUENCE OF ACTINISM. By ALBERT R. LEEDS, of Hoboken, N. J.

In a paper published in the Philosophical Magazine for June, 1879, I have given a brief review of the controversy as to whether potassium iodide, in very dilute solution, is decomposable by sulphuric acid. I likewise pointed out that the explanation of the opposite views, entertained by experimenters upon this question, was due to their having overlooked the essential part played by air or oxygen in this reaction. This last was brought to view by Baumert', in the course of experiments by which he showed that Andrews?, in the famous investigation undertaken to prove that Baumert's hypothesis that electrolytic ozone is a teroxide of hydrogen3 was false, had himself fallen into an error. For Baumert showed that when a stream of electrolytic ozone has been deprived of all of its active oxygen, by passage through a neutral solution of iodide of potassium, it may bring about a liberation of iodine in an acidified solution, placed later in the series, many times greater (from four to ten in the experiments tried) than that effected by the ozone itself in the first instance. So the curious fact remains, that while Andrews' main conclusion is true, all the results by which he succeeded in establishing it are affected by a constant error and are in excess of their true values. The triumph of Andrews' opinion (1856), that ozone contains no hydrogen whatsoever, but in its substance-matter is identical with the matter of ordinary oxygen, probably explains why the permanently valuable part of Baumert's work has been generally lost sight of; and why the erroneous method, of titrating ozone with an acidified solution of potassium iodide, has been persisted in even down to the present day. Ten years after the facts above stated were made known by

1 Pogg., Ann., XCIX, p. 88.

2 R. Soc. Proc.. VII, p. 475; Pogg., Ann.. XCVIII, p. 435.

Phil. Mag., VI, p. 51; Pogg. Ann., LXXXIX, p. 38.

Baumert, they were rediscovered by Payen 4, who extended their application to the action of nitric, acetic, oxalic and other acids upon dilute solutions of potassium iodide, in and out of contact with air.

In former papers 5, a summary of which is given in the Phil. Mag. (loc. cit.), I have shown that the presence of oxygen not merely facilitates, but is absolutely essential to, the occurrence of the reactions in all cases, and whether the reaction occurs in open or closed vessels, in the heat or cold, in darkness or in light. The only exception to this law is in the case of an acid like nitric, which, under the influence of light (the action of heat alone in the absence of light and oxygen is being investigated), spontaneously breaks up, and supplies by internal change the essential oxygen. The experiments made to determine the rates of decomposition, when various iodides in the presence of different acids were submitted to the influence of the magnesium, electric and solar rays, were made with solutions of known though not of chemically equivalent strength. To supply this defect a new series of experiments were performed immediately after the publication of those cited above, and it is to make known certain remarkable laws of actino-chemical change deduced from these latter experiments, that the present article is written.

The solutions were of such strength that 1 cc. of each of the acids employed was chemically equivalent to 12.6 cc. of a normal caustic soda solution; the iodides were each exactly equivalent to the 20 per cent. solution of the potassium iodide. 1 cc. of the iodide and 1 cc. of the acid were used in each trial, the volume of the test being made up to 100 cc. by the addition of distilled water. The tests were contained in "comparison-tubes" made of thin, perfectly colorless glass of uniform bore and dimensions, which were supported on frames in such a manner that each tube should be normal to the incident rays, and in the case of the magnesium and electric lamps, six inches from the focus of the light.

The first set of trials was made to determine, whether the addition of starch as an indicator facilitated the decomposition under the influence of light, as had been originally supposed, or whether, as later on, there had been reason to think, it retarded the reaction.

O Compt. Rend., LXII, p. 254.

5 Proc. Amer. Chem. Soc., 1878, II, No. 4; Jour. Amer. Chem. Soc., 1879, I, p. 18; ibid., P. 65.