508 : MICROSCOPY. 
tion of mounted insects to London, which have been presented to 
the Queckett club by Mr. Curties. They are represented by 
Messrs. Curties, Ingpen, Loy, McIntire and others as well pre- 
served and satisfactory objects, free from cloudiness, air bubbles, 
or deterioration of tissue as well as from distortion of form. Not 
being flattened or eviscerated, they show to great advantage in the 
binocular microscope. A few had been soaked in potash solution, 
but these were the least satisfactory members of the collection. 
The largest and best part of the objects had been immersed in the 
medium without maceration or other preparation. The smaller 
insects were simply killed by immersion in ether and immediately 
transferred to the soft balsam; the larger insects were similarly 
killed in ether, then dried a few days under slight pressure i 
tween the leaves of a book, and afterward soaked in turpentine 
and transferred from that to balsam. The balsam containing t 
insects was kept in the tropical sun for some time, until all moist- 
ure was dissipated and the balsam had pervaded the whole of the 
tissues. The muscles and other internal and external organs, not 
having been disorganized by potash or in any other way, were well 
preserved and capable of inspection; and in many cases polarized | 
well. Small delicate insects which are difficult of preservation 0 
even of study in any other way, are most successful in this; seh 
for instance, aphides, small and frail diptera, hymenoptera, minute 
spiders, eggs, larva, pupa, ete. This method is of value not only : 
o the microscopist, but also to the entomologist, placing anm 
frail specimens out of reach of dust, mould, ants, and 
dangers which threaten dried specimens. a 
We have tried this method largely, both with thin balsam, 
with hard balsam dissolved in chloroform and in benzol, and pe 
succeeded with all. Probably experience will show that -i 
best adapted to certain objects. A water-bath is a good ar A : 
for the tropical sun. When the balsam is sufficiently hard wa 
jects should be mounted in it in glass cells. Doubtless the 88 
blast cells will prove to be adapted to this purpose. 
Measure ANcuLAR Aperture. — Mr. Wenham, in a 
gain accuracy in measuring the angular aperture of dry objec ith 
would like to cut off all stray light that might enter the lens T 
out being capable of forming an image, by placing over the: se 
_ tive a conical nozzle having a small aperture in its ap® 
