198 THE MICROSCOPE. 



To the Editor of The Microscope : 



Dear Sir — In the number of The Microscope you were so 

 good as to send me, I see an extract from the Scientific American, 

 "Tracings for the Lantern." Having adopted a similar method 

 for the purpose of demonstrating my own sUdes, I will just 

 quote you the plan as described by the Rev. Dr. Dallinger, who 

 claims to be the originator of the system. I have seen some of his 

 own slides, lent to me by himself, which are certainly beautifully 

 done, and show all the details in perfection. He directs that " you 

 should use finely ground glass and draw with a very hard pencil. 

 ***** Then shade as an ordinary drawing for 

 a tint ; wash it after the drawing is complete, and when the wash is 

 dry, breathe upon it to moisten it, and with a camel's hair brush, cut 

 shorter by about half than they usually are made in the hair, dab the 

 wash even. The drawing is now complete, but wants transparency ; 

 give this by pouring over (as the photographers do collodion) very 

 much thinned Canada balsam, prepared by dissolving it in benzine 

 until it is of the consistency of thin cream ; pour off the superfluous 

 balsam, reverse the slide, lay flat to dry, and cover with a plain 

 glass." You may draw direct from the camera by putting white 

 paper under the object. I have succeeded well with this plan. The 

 glass is supplied by Forrest & Sons, Lime street, Liverpool. The 

 manipulator should be careful to get an even film of balsam when 

 laying flat. Yours faithfully, 



Thomas Rutridge, 



London, England. 



Sphero-Crystals. — G. Kraus records the discovery of sphero- 

 crystals in Ftelea, Coniuin and yEthusa. In ptelea they occur in the 

 leaf only; in conium they are also found in the stem, flower-stalks, 

 fruit, etc., but in all cases they are found in the epidermis only.. 

 They generally have the form of hemispheres, and are attached to 

 the wall; they are radiate or even spined. They are insoluble in 

 either cold or boiling water and in dilute mineral or organic acids. 

 — Roy. Mic. Jour. 



