OBITUARY. 



George Shadbolt. 

 Died 6th May, 1901, aged 83. 



George Shadbolt was elected a Fellow of the Microscopical Society 

 of London in 1845, and was President for the years 1856-57. 



His first contribution to the Society was in October 1848. He 

 there described an instrument for cutting the circular discs of cover- 

 glasses, also a collecting stick for pond life. On March 20 and 

 April 17, 1850, he gave a description of M. Nachet's illuminating 

 prism, together with a formula for its construction. On April 17, 

 1850, Mr. Wenham described his improvements on the Nachet illu- 

 minating apparatus : first, by achromatising it ; secondly, by mount- 

 ing two of them opposing one another, oblique illumination in a single 

 direction was avoided ; thirdly, how by means of a silvered parabolic 

 mirror he had secured achromatic all-round illumination (it is inter- 

 esting to note that the first parabolic reflector made is in the Society's 

 cabinet of apparatus). On June 26, 1850, Mr. Shadbolt described 

 his annular condenser, which consisted of a ring of glass having 

 its upper edge bevelled and polished both inside and out ; this may 

 be regarded as a simplification of the Wenham parabolic mirror. On 

 March 19, 1851, he described his sphaero-annular condenser, an 

 instrument differing only from the glass paraboloid of recent times in 

 that its outer curve was spherical and not parabolic. The above 

 papers will be found in the Transactions of the Microscopical Society 

 of London, iii. 1852. 



Mr. Shadbolt also wrote upon diatoms, and on November 14, 

 1849, described the structure of Arachnoidiscus (illustrated pi. XI.). 

 In 1857 he had movable stops placed at the back of his objective to 

 cut down the aperture. This was done with the view of carrying 

 out some of the erroneous ideas of Dr. Carpenter, one of which was 

 that a wide-angled lens was only suitable for the examination of the 

 " surface markings on the Diatomaceae," and that, in order to render 

 the lens " useful for histological purposes," it was necessary to 

 reduce its aperture by a stop. (This is now known as a Davis 

 shutter.) In 1858 he introduced the paraffin lamp to the notice of 

 microscopists, an illuminant which for general purposes has never 

 been superseded. 



It was during the Presidency of Mr. Shadbolt that the Society's 

 screw was introduced. After this he seems to have retired from active 

 microscopical work for about 20 years, but in 1876 he contributed a 

 letter to the Monthly Microscopical Journal controverting a statement 

 of Dr. Pigott's concerning the identity of chromatic and spherical 

 aberration. His last communication appeared in the Journal of the 

 Koyal Microscopical Society, iii. (1880) p. 1089, in which he joins issue 

 on the aperture controversy which was raging hotly at that time. 



With one exception Mr. Shadbolt was the senior Fellow of the 

 Royal Microscopical Society. 



