142 



SCIENCE. 



[Vol. XIX. No 475 



might not exert the same educational influence in New York 

 as IS put forth by the Royal Institution of Great Britain 

 in London, in which a course of as many as eighty lectures 

 of more or less popular interest has been given in a single 

 season. 



The brief experience which the Scientific Alliance has 

 already had has convinced the members that a still closer 

 union of the societies is necessary to the most effective ac- 

 complishment of their purpose, and this feeling has taken 

 the form of an earnest movement for obtaining a permanent 

 building as a home for all the societies. A building commit- 

 tee was appointed in October last, and has held several meet- 

 ings and done much towards developing plans for the accom- 

 plishment of the object mentioned. 



lo the main these plans embrace the idea of the erection 

 of a building, in the central part of the city, large enough 

 to afford each society rooms for its ordinary meetings, for its 

 library and collections, as well as facilities for research, and 

 also to contain a lecture-hall, capable of seating twelve 

 hundred people, to be used by all the societies in their public 

 work. It is part of the aim of the Council to obtain, ulti- 

 mately, if not at once, in connection with the proposed build- 

 ing, a fund for its maintenance and for the endowment of 

 original research and publication. 



It is hoped and believed that at this time, when public 

 spirit appeal's to be undergoing a revival in New York, and 

 numerous worthy objects are receiving generous aid and es- 

 tablishment by men of wealth, the cause of science will not 

 be overlooked or neglected. Music and other fine arts and 

 various charities have recently received munificent assistance 

 in the very direction in which the Alliance is looking for 

 aid, — namely, the erection of buildings suited to their par- 

 ticular needs, — and it seems reasonable to think that the 

 man, or men, will soon be found with sufHcient appreciation 

 of scientifl-C research, for both its educational and its prac- 

 tical value, to place it in a position as solid and substantial 

 as that now likely to be occupied by the fine arts and by 

 /organized benevolence. 



ACTINISM. 



On studying the nature of the action of the blue, or rather 

 the violet, ray of the spectrum, it appears to me to be a mis- 

 nomer to refer to it as chemical. The absorption of heat 

 attends chemical decomposition, and on the other hand the 

 disengagement of heat is the accompaniment of chemical 

 combination. We read in Professor Wurtz's excellent treatise 

 on " The Atomic Theory: " " It is heat which sets the atoms 

 in motion; they have absorbed heat in separating from each 

 other, since the rupture of the molecular equilibrium which 

 marks the end of the state of combination has required the 

 consumption of a certain quantity of heat. The beat thus 

 absorbed has restored to the atoms the energy which they 

 possessed before combination, and which represents aflfinity. 

 This heat is lost again whenever the atoms, passing into the 

 sphere of action of other atoms, fix the latter in some manner 

 or are fixed by them so as to form new systems of equi- 

 librium — that is, new molecules — in which henceforth 

 their vibration and motion are preserved. This action is 

 reciprocal." If with this we compare what takes place in 

 the so-called chemical action of the violet ray, we find a 

 great difference. The latter process is usually referred to as 

 one of decomposition and not of combination, and, in fact, 

 photography is'based on the property possessed by light of 

 decomposing chemical compounds by its reducing action. 



It is true that this decomposition is supposed to be attended 

 with certain chemical changes, as is the case also with the 

 decomposition of amyl and other vapors in Dr. Tyndall's 

 very interesting experiments in cloud making, although there 

 appears to be some doubt as to the nature of the changes. 

 Moreover, in the action of the violet ray on a mixture of 

 chlorine and hydrogen gases the formation of hydrochloric 

 acid would seem to be due to the operation of chemical affin- 

 ity. Nevertheless, when we consider the analogy between 

 this case and that of the formation of water by the passage 

 of a current of electricity through a mixture of oxygen and 

 hydrogen gases, a question may be raised as to whether the 

 former is due to strictly chemical action. The phenomenon 

 of electrolysis, in which the electric current decomposes a 

 molecular compound, is, moreover, analogous to that of the 

 decomposition of chemical compounds by the actinic action 

 of the violet ray. The latter phenomenon answers to the 

 decomposing action of heat, and the former to the combina- 

 tion of elements which attends chemical action; but they are 

 not the same. This is evident from the fact that, while in 

 the one case the combination precedes the discharge of 

 heat on which decomposition depends, in the other case it 

 follows decomposition. 



Nevertheless, in all cases actinic action would seem to be 

 attended with the aggregation of at least one element of the 

 decomposed ciiemical compound. Thus, when on the ex- 

 posure of chloride of silver to the action of light the chlorine 

 is expelled, the silver is precipitated. The result depends on 

 the instability of the equilibrium of chemical combination in 

 the presence of certain light-rays, and it is thought that all 

 substances are thus more or less affected by light. It is 

 found that the red rays are chemically inactive, and of the 

 others the absorbed rays are those which bring about the de- 

 composition which is the basis of actinic action. The liquid 

 nitrite of amyl allows the transmission of the yellow rays, 

 and Dr. Tyndall states that the blue rays, as complementary 

 to the yellow, are absorbed, and therefore that they produce 

 the "chemical" effect. As a fact, however, the complemen- 

 tary of yellow is violet, and tlie greatest actinic action is in 

 the violet ray, and it extends far beyond into the invisible 

 rays. This in itself would seem to prove that actinism is not 

 chemical action, as the intimate relation between this force 

 and heat would lead us to expect the association of chemical 

 action with rays towards the red end of the spectrum. The 

 vibrations of heat are atomic and not molecular, and possibly 

 this fact may have influenced Dr. Tyndall in his opinion 

 that the absorption of the actinic rays occurs in the main 

 within the molecule, and are not the act of the molecule as 

 a whole. There is no reason, however, why the absorption 

 should not be of the whole molecular mass; that is, of the 

 body of molecules that make up the mass, just as the absorp- 

 tion of heat is that of the atoms which make up the mole- 

 cule. 



Here would seem to be the real explanation of the phe- 

 nomena of actinism, which is a distinct power of light due 

 to its activity as a molar energy, just as heat is an atomic 

 energy. The combination which follows the decomposition 

 effected by actinic action has a similar relation to chemical 

 combination. The latter is atomic, whereas the former is 

 molar, as it affects the mass, and this through its molecules 

 and not through the atoms of- which these are composed. 

 From the fact that the electric light contains a large propor- 

 tion of actinic rays, and that the electric spark in rarified air 

 is diffused and of a violet color, it might be supposed that 

 actinism is only a phase of electricity. That they are closely 



