37 



wei'e exhibited illustrating the use of the rays for showing 

 diseases of the bones, such as necrosis, periostitis, and tubercu- 

 losis, also hip disease. There were also some radiographs of the 

 lungs, showing cavities and thickening in the lung tissues. 



The Lecturer then explained the methods of measurement 

 and localization. This is done by taking two or more radio- 

 graphs from different points of view, and noting accurately the 

 position of the tube with regard to the body containing the 

 hidden object. By constructing a figure with lines showing the 

 path of the rays, the size and position of the hidden objects can 

 be readily shown. These methods are used for the localization 

 of needles, shots, &c., in the hands and feet, and, where ne- 

 cessary, for stones in the kidneys. 



Some stereoscopic pictures were shown at the conclusion 

 of the lecture, by the aid of some Wheatstone stereoscopes. 

 These included radiographs of a rat, and of a mole, giving the 

 appearance of a solid body of transparent material, through 

 which the structure of the skeleton could be distinctly seen. 

 Similar effects were given by radiographs of some shells. As 

 illustrating the possible application of the rays for botanical 

 investigation, radiographs of some nuts were exhibited, showing 

 some with unsound kernels, some without any, or with only 

 imperfectly developed kernels. 



WEDNESDAY, MAY 10th, 1899. 



BY 



Mr. henry DAVEY, Jun. 



AT the outset Mr. Davey made allusion to Darwin's theory of 

 evolution as compared with Newton's theory of gravitation, 

 but without discussing the respective importance of the two 

 theories, or the priority in genius of the two philosophers, turned 

 to the contemplation of the prodigious change effected in thought 

 by the labours of Sir Isaac Newton, " who at the age of 45 pub- 

 lished the greatest of all scientific works, and then lived 40 years 

 longer without producing anything of special importance." 



