PROJECTIONS. 29 



bees and wasps. Antennae of moths and mosquitoes. 

 Fibres of cotton, woolen, silk, etc. Ferns, moss, lichens, 

 leaves of trees. Thin sections of wood. Small flowers, 

 stamens and pistils, pollen. Mites in cheese. Butter- 

 flies, beetles, animalcules in stagnant water. Vinegar 

 eels. Crystallization of camphor, sulphate of copper, 

 and most solutions of crystallizable substances. 



Diatoms, and indeed most objects that are prepared 

 for the microscope, appear to good advantage upon a 

 screen. Any book upon the microscope will have 

 many valuable hints upon obtaining and preparing ob- 

 jects in a suitable way, and will be a very useful book 

 to one interested in natural history but who cannot af- 

 ford to buy a good microscope. 



OUTLINE DRAWINGS FOR PROJECTION. 



Every one who uses either a lantern or the porte 

 lumiere for purposes of instruction, will need to make 

 outline pictures to illustrate his subject, as it will be fre- 

 quently impracticable to get a photograph of what is 

 wanted. Moreover, a simple outline is often quite suf- 

 ficient for the illustration, as, for instance, superposi- 

 tion and inclination of strata in geology ; sections of 

 machines ; writing, or musical notes j outlines of leaves, 

 roots, parts of a flower, insects, maps, etc. 



The surface of transparent glass is so smooth that it 

 cannot be marked with either common ink or a lead 

 pencil. If the glass be ground, so that a pencil will 

 mark it, it becomes so opaque that but little light can 

 go through it ; hence, a surface must be prepared which 

 will be transparent and yet allow marking upon it. 

 This can be effected in many ways, and I give a num- 

 ber which I know to be practicable : 



I. If a piece of glass be rubbed on one surface with 



