New Paraboloid Illuminator, dec. By James Edmunds, M.D. 85 
are, moreover, if well made, as manageable in practical work as 
they are perfect in optical principle. So far as I am aware, no 
previous appliance has ever converged upon an object unrefracted 
high-angled all-round light, so as to make it appear in the field of 
our best modern immersion-objectives as a brilliant shadowless 
picture floating in black space, like a star in the field of the re- 
flecting telescope. In any case, those who have more time and 
ability than myself for microscopic manipulation will give to this 
appliance such welcome and development as it may deserve. 
Note II. On the Resolution of Podura Scale by means of a New 
Paraboloid Illuminator. 
By James Edmunds, M.D., M.B.C.P. Bond., &c. 
( Taken as read before the Royal Microscopical Society.) 
I have a large and finely marked Podura scale mounted upon an 
ordinary slide, and covered with • 003 glass. Placing this upon 
the new paraboloid, I find that by the aid of Powell and Lealand’s 
twenty-fifth, sixteenth, and new immersion-eighth — working the 
scale up to about 2500 diameters under careful illumination from a 
white sunny cloud — the markings are, at various stages of the 
amplification, resolved into beautiful plumules or featherlets which 
appear to be exactly analogous to the scales upon the wing of a 
moth or butterfly. Each plumule stands out distinctly in fine 
definition, and is beautifully lighted up all round as if from above, 
while one looks down between the plumules on to a blue-black 
hyaline membrane from which the plumules spring— all the rest of 
the field being bistre-black. One can also see that the serrated 
margin of the scale is due to the overlapping of the ends of the 
plumules. This test-scale measures nearly the inch in extreme 
breadth, and fully the inch in length without the pedicle. The 
‘‘ test-scales ” only differ from the other scales in that the feather- 
lets are more finely developed, and I find that I can show the 
featherlets on almost all the scales irrespective of size. The 
rounded ones have their featherlets more like hairs, and they are 
often disposed in a vorticose manner, whereas the elongated test- 
scales have fully developed featherlets mostly disposed in a direction 
parallel to the long axis of the scale, and therefore not shadowing 
each other so much in the picture formed by transmitted light. 
At one or two points where my scale has been blistered by the 
focus of the paraboloid, or has in some other way been damaged 
while under this work, the bare membrane of the scale can be seen, 
and on the black field some torn-off plumules may be distinguished. 
When I first observed the abraded portions of the scale, it appeared 
