184 NOTES AND MEMORANDA. 



neous motion will bo found ludicrous in the extreme. A friend of ours 

 substituted a jointed toy suspended from the sash-fastener by an india- 

 rubber string, and he describes the eifect when it was set going as 

 comical exceedingly ! Nay, more, perfect pictures may be obtained in 

 each ocellus when the 1-inch condenser is used with a ^-inch objective. 

 A group of trees at some little distance from the window may be thus 

 sharply depicted, their leaves and branches waving in the wind ; and 

 the writer has had a panoramic view of blue sky with white clouds, 

 minute but clearly defined, flying across, all multiplied 150 times ! 

 Many persons, however, object that these figures are not really 

 formed by the lenses of the eye itself, but that any image presented 

 to it is merely repeated in it by refraction. When an objective is 

 used beneath as an achromatic condenser, this doubt not only seems 

 plausible, but it is impossible to disprove it directly. Still it is easy 

 to show the optical completeness of the ocelli, and that their lens- 

 like action is an absolute fact. To do this, set the microscope hori- 

 zontally, and then raise the fore part of the stand so that the axis of 

 the body is in a line with the upper part of a window five or six yards 

 distant. The mirror being removed, there will then be absolutely 

 nothing behind the " eye " but the slip of glass on which it is 

 mounted, yet with a ^-inch or ^-inch, the steel pen will show clearly, 

 and with the ^-inch a picture of the window, with curtains, tassels, &c, 

 and even objects outside, will be seen in each corneule, though small 

 and rather indistinct. If a large profile face or figure is cut out of 

 brown paper and stuck on a window-pane, it will show very well ; or 

 if a person stands on a chair against the light and raises the hands to 

 the head, no one observing the effect could doubt for a moment that 

 the " eye" continues to perform the same work which it formerly did 

 during life. By lamplight our range is far more limited. The plane 

 mirror gives only a small speck of light in each of the corneules, 

 which with 1-inch appear like minute nodules of a dull red colour, 

 much resembling some of the thick discoid diatoms (Coscinodiscece, 

 Aulacodiscece, &c.) when viewed dry. The concave mirror produces 

 a troublesome image of the flame of the lamp. On parallelizing the 

 light by a bull's-eye, this image is got rid of, and the steel pen shows 

 very well with ^-inch or ^-inch, but to obtain really good effects the 

 1-inch must be used as an achromatic condenser, with bull's-eye and 

 concave mirror. Then the fly or similar objects (a small transparent 

 photo-portrait has been suggested) will come out admirably, but a 

 patient adjustment of all the appliances should be tried — of the lamp, 

 bull's-eye, mirror, and condensing-objective, as well as exact focus- 

 sing of the " power" employed. We read in the ' Monthly Micro- 

 scopical Journal,' No. 42, that at a soiree of the Croydon Microsco- 

 pical Club in November, 1871, Mr. Butler exhibited an eye of beetle 

 magnified 400 times (probably by a ^-inch and a highish ocular), show- 

 ing in every facet the moving seconds'-hand of a watch reflected into 

 it. We do not know the precise means by which this curious result 

 can be satisfactorily accomplished. If direct sunlight is allowed to 

 fall on the mirror when a low power (1-inch or ^-inch) is employed 

 on the " eye," beautiful and vividly-coloured geometrical patterns 

 are seen in it, changing like a kaleidoscope with every alteration in 



