HARDWICKE'S SCIENCE-GOSSIP. 



229 



long before the sun set. Alas ! it is very different 

 now, and what else could be expected, seeing the 

 wanton destruction indulged in, one collector boast- 

 ing that he had himself taken several hundreds, and 

 another more than he could " set " ? 



Fig. 139. Light Crimson Umlerwing {Cutocala promissa). 



leaves ; and next, the pertinacious attacks of two 

 most bloodthirsty flies — Heematopa pluvialis and 

 Chrysopis ccecutiens, to bear which will require a 

 skin as tough as leather and the patience of Job. 

 I well remember one hot sultry day in July, the 

 year before last, when after Valezina, my 

 brother, a friend, and myself were so beset 

 by these torments, that we gave up collecting 

 Lepidoptera in despair, and turned our atten- 

 tion for the while to Diptera. Swinging the 



c; a 



Fig. 141. Rosy Wave (Acidalia emutaria) a 



nets ' to and fro, we caught scores of these 

 flies ; then getting them into one corner of 

 the net, we wrung the net, and at the same 

 time their necks, if flies have necks, and 

 turned them out into little heaps, as a warn- 

 ing, we hoped to others ; but of no avail, 

 " the cry is still they come," so we were fain 

 to beat a precipitate retreat. 



Chichester. Joseph Anderson, Jun. 



Fig. 140. Dark Crimson Underwing (Catocala sponsa). 



As might be imagined, where the different kinds 

 of Ericaceae, grow so luxuriantly, heath-feeding 

 species turn up pretty commonly ; such as B. rubi, 

 Porphyria, and more rarely Agathina. There are 

 but two drawbacks of which I know to the plea- 

 sure of the collector in the New Eorest. First and 

 foremost, the water is vile, at least about Brocken- 

 hurst, tasting like a decoction of the rottenest 



AIR-BUBBLES" AND 

 IN FLUID. 



MOUNTING 



W 



HERE do they come from ? is a ques- 

 tion that has been often asked, but 

 never answered. It is no uncommon cir- 

 cumstance to find a slide, after it has been 

 mounted only a very short time, showing one 

 or more air-bubbles, although, to all appear- 

 ance, perfectly free from them when first 

 done. This has always been looked upon as 

 a great mystery ; yet, if we " infer the un- 

 known from the known," as suggested by 

 Faraday, we shall not be long in discovering 

 the truth. 



Being one of the earliest workers at the 

 "Electrotype," as it was then termed, we 

 were, at first, greatly annoyed by the newly- 

 formed metal being occasionally inseparably 

 united with the metallic mould upon which 

 it had been deposited ; but it was soon 

 discovered that the cause of separation 

 was due to a film of air being adherent to the surface 

 of the metal, and serving to prevent their adhesion. 

 On the other hand, when the metallic moulds had 

 been washed in hot water, or were immersed in the 

 fluid while warm, this film of air had been driven 

 off, and the metals adhered together as the conse- 

 quence. 

 If we drop a portion of water upon a glass slide, 



