August 1, 1S66.] 



SCIENCE-GOSSIP. 



1S7 



MICROSCOPY. 



Dissecting-Troughs— It 1 is now three or four 

 years since I was looking about for some cheap and 

 convenient vessel in which I could dissect insects 

 and other small animals that require to be examined 

 under water. I found fault with the earthenware 

 troughs used by photographers, because they were 

 expensive and liable to break, and with gutta-percha 

 ones because they would crack at the corners and 

 let the water out. One day the idea struck me 

 that the sardine-box I was emptying might be made 

 into the very thing I wanted ; so, having cleaned the 

 box (an operation easy to perform if the oil is first 

 saponified by a solution of soda or ammonia), I 

 cut the rim off with a strong pair of curved lamp- 

 scissors, and my dissecting-trough was complete. 

 I now keep by me several of these troughs of dif- 

 ferent depths. For pinning-tablets I use either 

 cork or was, and it is convenient to have them 

 separate, so that you can put them in or lift them 

 out after the animal is pinned down. The tablet 

 must, of course, be weighted; and this is con- 

 veniently done by securing it with thin wire to a 

 piece of sheet lead. I am induced to make this 

 trivial invention more widely known, because I feel 

 sure that by simplifying necessary apparatus we 

 increase the number of investigators. Only the 

 other day I met with a young entomologist, who, 

 though he knew more about insects than the ma- 

 jority of the colour-distinguishing insect-catchers 

 that go under that name, still had never attempted 

 to examine their internal structure. I found he 

 thought, as many do, that the inside of an insect 

 was only to be made out by an advanced anatomist, 

 and that to others it was a mere "squash." He 

 was surprised to find how easy it was to see all the 

 parts that are so vaguely written about. When he 

 set to work for himself, his great difficulty was to 

 get something to serve the purpose of a dissecting- 

 trough. I told him of my sardine-box troughs ; he 

 thought it a " splendid idea," and forthwith bought 

 some sardines, and made all his friends eat them 

 till the box was empty. Three days afterwards I 

 ' saw in his sardine-box a more instructive dissection 

 of a caterpillar than is to be found in any museum 

 with which I am acquainted. But I have not done 

 with the sardine-boxes yet ; for a Welsh friend of 

 mine, an experienced fly-fisher, has found a use for 

 the brass-foil labels. He first carefully crinkles 

 them up, so as to produce a many-facetted surface, 

 which more easily catches the light, and then on 

 certain days, when the fish take no notice of ordinary 

 flies, he puts a small piece of the foil round the 

 fly's body. This, he says, often enables him to kill 

 his dish of trout when other fishermen have spent 

 their day without a rise.—/. Gedge, Cambridge. 



To Capture Podur^:.— A short time ago I dis- 

 covered a number of Podurce on the window-sills at 

 the back of my house, about two feet from the 

 ground : they appear to take up their abode in the 

 crevices of the bricks, and the small openings on 

 the underside of the sill, and come on to the upper 

 surface in search of food. I sometimes meet with 

 them in groups of three or four, but more frequently 

 individually. My mode of capture is as follows :— 

 I take a tumbler or top of a wine-glass, and quickly 

 place it over them ; then gradually get them into the 

 centre of the space covered by the glass, and raise 

 one side a little, and puff in a volume of tobacco 

 smoke, immediately dropping the glass to confine 

 it ; the little prisoners will be seen to jump about 

 in'a most frantic manner for three or four seconds, 

 then suddenly drop clown on their backs and stretch 

 out their tails, apparently dead; the glass can then 

 be removed, and the little victims transferred to a 

 pill-box until required for use ; but be very cautious 

 when you open the box; for the first lot I caught 

 in this way I put in a box, not requiring them 

 for three or four days, when I opened the box, 

 and to my astonishment they were all alive again, 

 although the morning after I caught them (about 

 twelve hours after being submitted to the smoke) 

 they were still dead to all appearances : another 

 gentle dose of smoke effectually killed them— /. R, 

 Clapham. 



The Stanhoscope— The paragraph in the July 

 Science Gossip on the use of the Stanhoscope m 

 gathering marine Diatomacese has been the means 

 of inducing scores of your readers to apply to me 

 for the small optical instrument there referred to. 

 As no printed explanation of the mode of using the 

 lens accompanies it, some of the purchasers have 

 been at a loss to understand how it ought to be 

 used. I therefore request permission to state 

 briefly that the cap containing the lens should be 

 taken off; that the objects to be examined should 

 be placed on the square end of the lens ; that the 

 cap should be replaced, and the object be looked at 

 through the apparatus, placing the eye near the 

 curved end of the lens. The magnifying power is 

 so high, that only small objects can be observed by 

 means of the instrument, and the best and simplest 

 mode of testing its power is to place on the square 

 end of the lens some of the dust from the wing ol a 

 butterfly or moth. The method for examining 

 Diatomacese, is to place a very small portion of the 

 fluid containing the diatoms on the flat end ol the 

 lens, and look through it towards the light, as 

 before described— T. P. Parkas. 



Preparative Fluid. - M. Chevalier in his 

 Etiuliant Micrographe, recommends the use ot the 

 essence obtained by distilling Canada balsam as 

 preparing objects more perfectly than any other 

 fluid, for mounting in the balsam itself. 



