110 MEMORANDA. 



all other means had failed to unravel the mystery of the 

 composition of this concretion. I macerated a portion of it 

 for some time in distilled water, expecting to detect 

 the starch granules of the oat by the polarizing apparatus of 

 the microscope, but in this I failed. 1 continued the mace- 

 ration, separating the parts a little with very fine needles, 



and at last was able to detect very beautifully masses of the 

 hairs of the palea of the oat, of which, and the husks of the 

 oat, the concretion seemed to be entirely made up. 



I need say no more, the value of the microscope in this 

 case is undeniable ; and I have only to present you with a 

 slide and a drawing of the analysis for your own inspection. 

 — H. MuNROE, M.D., Hull. 



On Microscopic Apparatus. — Allow me to call your atten- 

 tion, and that of yovir readers, to two little contrivances of 

 mine, as they may be found useful. 



The first is a simple apparatus for illuminating objects 

 under the microscope ; and will be found particularly of use 

 when examining Diatomaceae. Knowing that there are many 

 microscopical observers like myself, not able to expend large 

 sums in accessory apparatus to the microscope, I particularly 

 recommend it to their notice. 



It consists of a plate of glass (s, fig. 1) (an ordinary slider), 

 three inches by one ; to one side of which, in the centre, is 

 attached, by Canada balsam, a plano-cotivex lens (l), and this 

 may be of about one quarter-inch focus. Lenses of different 

 powers can be used, although I have found one of half-inch 

 and one of a quarter-inch focus to be the most useftil. The 

 way in which this is used is seen in the first figure. The 

 rays of light (r) fall on the lens (l), placed on the microscope- 

 stage (k), so that the flat side is uppermost, upon which is 



