1853.] 523 



7. Limestone with sulphuric acid, pale brown to the thickness of 

 cardboard, beneath slightly coloured. 



8. Carbonate of iron with sulphuric acid, black to the depth of a 

 quarter of an inch. 



9. Nitrous acid, dark brown more than the eighth of an inch 

 deep, beneath yellowish brown. 



10. Nitric acid mixed with exposed ozone powder, blue-black to 

 the sixth of an inch deep, below that reddish brown. 



11. Nitric acid mixed with unexposed ozone powder, blue-black 

 to the sixth of an inch deep, below that reddish brown. 



These experiments may require some modification, yet they point 

 out the fact that striking differences are apparent, differences which 

 must open up a new method of investigating ozone. 



Not only have the tests hitherto used been made without due re- 

 gard to the pureness of the chemicals and fitness of the material 

 used, but the paper box in which they have been kept is not sufficient 

 for their perfect preservation ; a dark, dry, air-tight box is essential ; 

 and this should not be opened in a room where there is iodine, 

 chlorine, nitric acid, phosphorus, hydrochloric acid, or other che- 

 micals likely to be injurious to the tests. I am now manufacturing the 

 tests, which will be distributed by Messrs. Negretti and Zambra, and 

 I have constructed a proper box in which in future they will be sent. 



II. {( On the Equations of Rotation of a Solid Body about a 

 fixed Point." By WILLIAM SPOTTISWOODE, M.A., F.R.S. 

 Received March 21, 1863. 



(Abstract.) 



In treating the equations of rotation of a solid body about a fixed 

 point, it is usual to employ the principal axes of the body as the 

 moving system of coordinates. Cases, however, occur in which it 

 is advisable to employ other systems ; and the object of the present 

 paper is to develope the fundamental formulae of transformation and 

 integration for any system. 

 The integrals found are 



cos an, 



) , 



