196 BRITISH CICADiE. 



bichloride will keep tragacanth-mncilage, in stopped 

 bottles, free from fermentation for many months.* 



Naphthaline, melted and cast into small blocks, will 

 be found very efficacious in preserving museum speci- 

 mens from both mites and mildews. 



Some regret must be expressed that it has not been 

 possible to draw the figures on my plates magnified to 

 one scale. Obviously the same amplification necessary 

 to bring out the details of a small Eupteryx, if employed 

 to figure a Centrotus, would wholly fill one plate. The 

 amplification given by a 3-inch objective is too great 

 for all large species ; and a combination to form a 

 focus of 4 or 4-|- inches, even if such would suit the 

 stage of the microscope, would be somewhat difficult 

 to acquire. 



I have found the following adaptation very con- 

 venient, when the camera lucida is to be used ; and it 

 involves little or no expense from the optician. 



A double concave spectacle lens may be chipped into 

 a circular form, fixed in a short tiihe or collar, and 

 then temporarily slipped over the nose of the weakest 

 objective. The focal length of the objective then will 

 be increased, and, if required, it may be still more 

 lengthened by placing another fragment of spectacle 

 lens in front of the former piece. 



Such a combination of course is not optically per- 

 fect ; but for most purposes, such as for drawing, the 

 method will be found both practical and efficient. 



* To do away witli the annoyance of broken corks and sticking 

 stoppers to bottles containing gnms, A'aruislies, and the like, small pieces 

 of window-glass, of three-quarters or one inch square, may be pressed on 

 the open necks of the phials. If moistened with the gum or varnish 

 they will effectiTally close the bottles, and their removal is very easy by a 

 knife. 



