11 



stations. They consisted of barometers, thermometers, psychrometers, 

 and magnetometers which registered their variations by means of 

 photography. His method obtained the preminm offered by the 

 Government for such apparatns, as well as a Conncil Medal from the 

 Jurors of the Great Exhibition. These instruments record auto- 

 matically, by very beautiful arrangements, the continual changes in 

 the dip and declination of the needle, and in the intensity of the 

 magnetic force. This could not be arrived at by any amount of per- 

 sonal observation ; and the movements of a spot of light upon the 

 revolving sheet of chemically prepared paper are more to be trusted 

 than the perceptions of the human eye. The adoption of these 

 instruments at the Greenwich Observatory rendered it possible to 

 reduce the staff of assistants and to dispense with night duty, while 

 they revealed magnetic disturbances of a character which otherwise 

 would probably have escaped notice. The perfecting of these 

 apparatus involved many considerations both of a mathematical, 

 physical, and chemical nature, which will be found detailed in the 

 " British Association Reports," from 1846 to 1849, and in the 

 "Philosophical Transactions " of 1847, 1850, and 1852. 



Mr. Brooke also studied the theory of the microscope, and was the 

 author of some inventions which facilitated the shifting of lenses, and 

 improved the illumination of the bodies observed. He also applied 

 his improved methods to the investigation of some of the best known 

 test objects of the microscope. (See "Proc. Roy. Soc," vol. vii, 

 p. 139.) In later years his papers were of a more theoretical character, 

 bearing upon the dynamical theory of electricity, on the nature of 

 electric energy, and on the supposititious character of that ether which 

 is assumed to pervade all matter and space. These are to be found 

 principally in the "Phil. Mag." for 1866, and in the "Proc. Roy. 

 Soc," vol. xv. He was also the author of various papers and lectures 

 bearing on the relations of natural science and religion. 



He is, however, most popularly known by means of the " Elements 

 of Natural Philosophy," originally compiled by Dr. Golding Bird, but 

 which after the death of that physician was re- written and enlarged 

 by Mr. Brooke on bringing out the fourth edition. Since that time 

 new editions have been constantly called for ; the results of more 

 recent discovery have been carefully added, and the book has remained 

 a favourite introduction to the study of the physical sciences, 

 especially in the medical schools. 



Mr. Brooke died at Weymouth on the 17th of May, 1879, leaving a 

 widow and family, and many friends who recognized him as one of the 

 most kindly and modest of men. He will be remembered on account 

 of his pleasant conversation, or his thoughtful advice, or the quiet 

 influence of his private life, by many who knew little or nothing of 

 his varied acquirements and ingenious inventions. 



