AeCESSOEY INSTEUMENTS. 



147 



sented by fig. 102, as being less liable to interfere with direct 

 definition, and also readily made, out of a piece of small flat 

 steel wire. 



Bonnet or Hood for the Compound Body. — For the purposes 

 of drawing, or when an object has to be carefaUy examined 

 for a long time by lamp-light, in order to screen the eye as 

 much as possible from all extra illumination, an apparatus, 

 termed the hood or bonnet, has been contrived by Mr. Lister. 

 It consists of a shade made of four or more pieces, either of 

 cardboard or pasteboard, painted black, or'else covered with 

 black cloth or velvet : it is of an oblong figure, and the central 

 portion fits upon the eye-piece or upon the end of the compound 

 body close to it, whilst the remaining three pieces turn up to 

 form the sides; sometimes there is a place cut out for the 

 nose to fit into. When this instrument is used, no light or 

 heat can come near the eyes but that reflected through the 

 compound body by the mirror ; all glare, consequently, is taken 

 away. Mr. Lister's hood is very portable, the sides fold down 

 upon the centre-piece, and then it occupies a very small com- 

 pass. Mr. Leonard has constructed a convenient form of hood 

 of paste-board and light wood ; a front view of this apparatus 

 is represented as applied to the microscope in fig. 103, and a 

 back view in fig. 104. The forehead is surrounded by the 



circular top of paste- 

 board covered with 

 thin leather, attached 

 to a piece of light 

 wood, into which the 

 end of the eye-piece 

 of the compound body 

 is made to fit ; this 

 part is covered with 

 black paper, and two 

 depressions are made 

 in it for the nose, one 

 on either side of the 

 Fig. 103 compound body, in 



order that the ob- 

 10* 



