294 Professor Horsford on the Relation of the 



clined, apparently from forces acting laterally, or from below ; 

 but which forces, from the undisturbed condition of the sur- 

 rounding beds, could not have acted in such a manner as to 

 have produced the disturbance referred to : they must there- 

 fore be accounted for by peculiarities or changes in the method 

 of deposition, and by subsequent changes. 



Professor Hall stated that he had also accumulated con- 

 siderable evidence in regard to this subject, and regarded it 

 as highly important in a geological point of view. — (Proceed- 

 ings of the American Association for the Advancement of 

 Science.) 



Relation of the Chemical Constitution of Bodies to Light- 

 By Professor E. N. Horsford, of Harvard. 



Professor Horsford called attention first to the well-known 

 facts that the colour of the hair on animals varied, and was 

 more intense on certain portions of the body. The metals 

 also had colours which were affected by their composition. 

 The change of their colour in summer and winter was also a 

 well-known fact. He enumerated many metals which changed 

 their tints by the simple process of heating. These were 

 phenomena which ought to be investigated by means of 

 chemistry. The change of tint is without change in chemical 

 composition. The law appears to be that metals pass from 

 a lighter to a darker tint. The loss of water causes a change 

 from a lighter to a darker tint. In charring wood, we have 

 a change from a lighter to a darker tint. He illustrated on 

 the black board that blackness was the natural colour of all 

 non-gaseous bodies ; and he cited the series of compounds of 

 gold, silver, nickel, platinum, tin, and other metals. He illus- 

 trated how the compounds of the several metals, as they 

 became more divided in their molecular structure, varied. 

 He exemplified them by the series of compounds of lead with 

 oxygen, in which, as the oxygen prevailed, the colours be- 

 came lighter. This was in keeping with discoveries made 

 by Liebig, and other eminent chemists whom he named. 



Dr Draper had found the tints to vary in the order in which 

 the metals had certain affinities, as in barium, strontium, and 



