INJURIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 



4fi7 



C 





U50 



Fig. 474. — Instruments for ascertaining the exact dilution of 

 lime-sulphur. Beginning at the left, Baume hydrometer; specific 

 gravity hydrometer; hydrometer cylinder to hold liquid being 

 tested. (After Bausch & Lomb Optical Co.) 



