[14] 



fllMcroscopical 3niaocr^» 



By Dr. Royston-Pigott, M.A., F.R.S. Plate II. 



WHEN an object has been universally studied for half-a- 

 century without any clear conclusion as to its structure, 

 either a strong bias may be suspected or imperfect instru- 

 mentation, or feeble powers of observation. 



A familiar example is that much-vexed question, the markings 

 on such diatoms as J^ormosum, Angulatum^ Rhomboides^ etc. etc. 

 Fifty years ago they were called lined objects, from their appear- 

 ance under Ross's famous "quarters" giving 500 diameters. I 

 could only get lines. Topping and others showed me the same 

 appearances. It was not until I gave Powell and Lealand a commis- 

 sion to form for me three of their best glasses — ^, ^, and 1/16 — 

 regardless of expense, that a spherical structure appeared which 

 astonished me exceedingly, the lijies having entirely disappeared. 

 The next question arose, If the beads are hemispherical, can they 

 form optical positive images ? Having worked on this question for 

 many years, I now beg to present to our readers some of my results. 



I recommend to students patient practice on the images 

 formed by beetles' eyes (winged creatures' eyes fail to give the 

 proper images).* Everyone knows they are hexagonally formed, 

 like a honeycomb. I have succeeded on a clear day in displaying 

 the miniature of a church-steeple 400 yards distant. Next, a 

 minute hole, brilliantly illuminated, produces very striking positive 

 images, formed between the eye of the observer and the eye of 

 the beetle, as shown by delicate focussing. Its sidereal focus is 

 about I — 600th of an inch, and lies above the convex surface, 

 producing exquisite images of objects beyond. These simple 

 facts demonstrate convexity in diatomic markings and the exist- 

 ence of spherical bosses, 



A further advance in fine definition was attained by assuming 

 that the cell, seen in coarse diatoms, is also spherically formed. 

 My delight was extreme when the first miniature was descried. 

 Minute apertures in front of a brilliant flame now gave gorgeous 



* I am so informed by Mr. Hinton, who mounted for me a drone fly's eye, 

 which gives no images at all. The beetle here alluded to is the common 

 house cockroach. 



