Chemistry and Physics. 299 



context, readily appears to contradict the quotation from my 

 report on page 179. But there is no difference between Dr. 

 Peale and myself. When I wrote that chapter in 1874 I re- 

 garded the whole Lignitic group as forming the closing portion 

 of the Cretaceous. So I considered the period of accelerated 

 upheaval as occurring at the close of the Cretaceous, that is, at 

 the close of the Lignitic group. Dr. Peale places the action at 

 the same time. 



I have no additional facts to offer in support of the provi- 

 sional- conclusions which I offered in the report to Lieut. 

 Wheeler. All the material in my possession is given in that 

 report and the synopsis of that, which seemed to have a bear- 

 ing on the age of the system, is to be found in Wheeler, vol. 

 iii, Chap, xvil Nor am I likely to secure any additional facts 

 either pro or con, as there is no probability that I shall have an 

 opportunity to revisit the Eocky Mountains for a number of 



New York, March 9th, 1871. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 

 1. On the Velocity of Chemical Heactions—BoovsKX and 

 Kajaxder have continual th. «x } , in. it- .-mmm-i vd U flu; 

 former to ascertain the velocity of chemical reactions. Boguski 

 defines' velocity of reaction by supposing that u=f[a r/ 3 , " 3 , 

 a H , t), in which u is the quantity of the new body pro- 

 duced in the time t, and a„ «„, a 3 a. *e co 



der which the reaction takes place. Hence the first differential 

 coefficient, ^ /=(«,, a 2 , a % . . . a„ t) represents the reaction- 

 velocity under the conditions given. It remains to find the form of 

 the functions u and — . Since all the conditions must be exactly 

 measurable and expressible in numbers, the author chose for ex- 

 periment the action of 



bles-thet. fl ntr-vnti* snrfe 



acted on and the concentration of the solution. " t oncentration 

 is used to express the value given by the formula D.^.y-. lu 

 which D is the sp. gr. of the solution, p the percentage content of 

 Jbe body dissolved" and M its i:. ' the num- 



ber of molecules of this body in a unit of volume of tm 

 is directly proportional to this value, if V represent the volume 

 in e.c, the formula V.D.^.-^-=y represents the concentration 



