94 AN HOUR AT 



On principle, I very much dislike to see objects mounted with 

 an irremoveable black back-grotmd. When it is desirable to view 

 objects as opaque, there are so many other ways of doing this ; 

 e.g. — the diaphragm, or the dark-well of the opticians, or a piece 

 of dead-black paper, cloth, or velvet, placed behind the slide ; it 

 can then still be viewed as a transparent object also. Otherwise 

 it is the mounter saying to the observer — " You shall see my slide 

 as / will, and in no other way." 



■ TuFFEN West. 



Sphaeraphides of Cactus were obtained from Mr. Peacock, of 

 Hammersmith, who imported a very fine specimen, but it fell to 

 pieces in travelling ; he very generously distributed the pieces 

 for the benefit of Microscopists generally. 



These Sphaeraphides required no maceration ; a little grating 

 together, or merely rubbing with the finger, is sufficient to reduce 

 the tissue to powder, and the Sph^raphides are easily separated 

 by allowing them to roll down a sheet of writing paper. The 

 little balls readily separate from the remaining debris, and the 

 process may be repeated once or twice if necessary. They show 

 much the best with a little light from below, or with spot-lens. 



H. E. Freeman. 



Turkey Rhubarb.— Just one passing observation as to Mr. 

 West's suggestion that we should look for Sphaeraphides in Hhei 

 Pulv. I have read that real Turkey Rhubarb is scarcely ever 

 seen now, and that the best houses have ceased to quote a price 

 for it in their lists. Mr. West speaks of the " dressed-up Engfish" 

 Rhubarb, and this reminds me that the dressing is, or used to be, 

 one of the indications of quality. If my memory serves me, the 

 Turkey (real) or Russian used to be always clean-cut with a knife, 

 and therefore the edges, or " arrises," were left sharp, or at least 

 angular ; but the East Indian variety, which is much inferior in 

 quality, and much lower in price, is, or was, always finished with a 

 file, and consequently presented no " arrises," although it is thus 

 made to look neater to the eye of the purchaser. Sphaeraphides 

 are not plentiful in the E. I. Rhubarb. 



W. Lane Sear. 



Dark-g^round Illumination.— I find that many objects show 

 better, not with a black, but with a white or porcelain back-ground, 

 and it is useful to have the following slips of glass, of the same 

 size as slides, both for opaque and transparent objects : — 



JPale Blue, for destroying the yellow glare of the lamp. For 

 transmitted light. 



