47 



CHAPTER OF VARIETIES. 



ON THE YELLOW COLOUR OF ANIMALS AND PLANTS. It is a CU- 



rious fact, that animal and vegetable yellows should be so much more 

 premanent than all other colours. The yellow of the petals of flowers is 

 the only colour which is not discharged by the fumes of sulphureous 

 "acid. If a lighted match be held under a flower, heart'sease ( Viola 

 tricolor) for example, the purple tint will instantly disappear, but 

 the yellow will remain unchanged : the yellow of a wall-flower (Chei- 

 ranthus fruticulosus) will continue the same, though the brown streak 

 will be discharged. I have noticed this in a variety of other flowers. 

 Yellow dyes are also more permanent than most other dyes ; and in 

 the above cited instance of the goldfinch, (page 24,) the yellow on the 

 wings continued unchanged, while the rest of the plumage was turned 

 black. EDWARD BLYTH. 



Tooting, Surrey, Dec. 3d, 1832. 



ON FLIES WALKING UP GLASS, AGAINST GiiAVITY. Sometime 



ago, Mr. Blackwall, one of our most ingenious and original observers, 

 read a paper to the Linnoean Society, adducing facts discordant with 

 Sir E. Home's opinion that flies walk up glass by means of a vacuum 

 produced in their foot, on the principle of the boys' leather-sucker. 

 I think it highly probable that Mr. Blackwall is not aware of 

 some of his views having been anticipated nearly two hundred years 

 ago. " The common fly," says Dr. Power, " hath six legs, but 

 goes only upon four ; the two foremost she makes use of instead of 

 hands, with which you may often see her wipe her mouth and nose, 

 and take up any thing to eat. The other four legs are cloven, and 

 armed with little claws or tallons (like a catamount), by which she 

 layes hold on the rugosities and asperities of all bodies she walks 

 over, even to the supportance of herself, though with her back down- 

 wards and perpendicularly inversed to the horizon. To which purpose, 

 also, the wisdom of nature hath endued her with another singular arti- 

 fice, and that is a fuzzy kinde of substance like little sponges, with 

 ivhich she hath lined the soles of her feet, which substance is also 

 repleated with a whitish viscous liquor, which she can at pleasure 

 squeeze out, and so soddcr and beglew herself to the plain she walks 

 on, which otherwise her gravity would hinder (were it not for this 

 contrivance), especially when she walks in those inverted positions." 

 EXPERIMENTAL PHILOSOPHY, PAGE 5. 4TO. LONDON, 1664. 



