78 Scientific Intelligence. 



10. Relation of the wave-length of light to its intensity. — One of 

 the most important questions in optics is the question whether the 

 velocity of light depends upon its intensity. Ebeht has under- 

 taken an elaborate study of this point. Interference fringes wore 

 employed, the writer showing that changes in wave-lengths 

 amounting to only -g-g-oVoo" °f their values, or changes in velocity 

 of light amounting to ±1*5 kilometers can be detected by this 

 method. Different sources of light were employed. It was found 

 that the wave-lengths and the velocity of light did not change a 

 millionth in value when the intensity of light varied from 1 to 

 250. — Ann. der Physik xind Chemie,' No. 11, 1887, pp. 337-383. 



J. T. 



11. Brief notice of a paper by Mr. HallocJc* entitled : The Flow 

 of solids, etc./ by W. Speing. (Communicated by the author.) — 

 I have shown, it will be remembered, by numerous experiments, 

 that solid bodies possess, to different degrees, the property of 

 being welded together, while cold, under a sufficiently strong 

 pressure. In compressing bodies of a different chemical nature I 

 have been able to obtain, at a low temperature, a number of com- 

 binations of bodies in a solid state, combinations which are, gen- 

 erally, produced only with the aid of a temperature more or less 

 high. These researches were undertaken with the view of decid- 

 ing whether it is possible to find in bodies in a solid state, any 

 trace of the peculiarities which especially characterize the liquid 

 state. 



I have also been led to state, as the result of my experiments, 

 since 1880, that " matter assumes, under pressure, a condition rel- 

 ative to the volume it is obliged to occupy,' " but this condensa- 

 tion is permanent only when the matter admits of different allotropic 

 states. Since then, new experiments,! still in part unpublished, 

 have made me recognize the importance of the part that a certain 

 degree of temperature plays in these phenomena, so that for 

 the solid state, as well as for the gaseous one, a critical tempera- 

 ture would be remarked, above or below which, the changes by 

 simple pressure would be no longer possible. 



The consequences of all this is, for instance, that liquid bodies 

 must pass under pressure into a solid state, taking of course the crit- 

 ical temperature, into account, if their specific volume is smaller 

 in a solid state than in a liquid one, and conversely. This con- 

 verse has been demonstrated first by Mouzon, since then by my- 

 self in cooperation with my friend J. H. van't Hoff. I had 

 intended verifying also the first proposition, but I have been 

 anticipated, to my great satisfaction, by M. AmagatJ who has 

 just produced the solidification of several liquids by the action of 

 pressure. The verification of the general result of my experi- 

 ments has given me great pleasure ; its value will escape no one. 



This taken for granted, I come to Mr. Hallock's article. 

 The author imputes to me the absurd idea that solid bodies 



* See this Journal, xxxiv, No.. 202, October, 1887, p. 277. 



f Zeitschrift f. phys. Chemie, i', p. 227. % Comptes Eendus, cv, p. 165, 1887. 



