DALE ON SPECIES AND VARIETIES. 355 



constantly exhibits the Will-with-the-Wisp, but having a very pale 

 colour. The flame appeared and disappeared, but was so mobile 

 that I could never approach sufficiently near to enable me to set fire 

 to any thing with it. 



In the course of the same year I visited a place at Walkenried, in 

 the Hartz, where these lights are said always to occur ; they were 

 very much like those of the Neumark, and I collected some of the 

 gas in a flask. On the day after, I found by experiment that it oc- 

 casioned cloudiness in lime-water, a proof of its containing carbonic 

 acid. 



I observed accidentally another phenomenon allied to this, at the 

 Porta Westphalica, near Minden. On the 3d August, 1814, we 

 played off a fire-work from the summit, to which we had ascended 

 during the dark, and where no ignis fatuus was visible. But 

 scarcely had we fired off the first rocket, when a number of small red 

 flames were observed around us, below the summit, which, however, 

 speedily extinguished — to be succeeded by others on the firing of the 

 next rocket. 



These facts induced me to separate the ignes fatui from the 

 luminous meteors, and to free them from all connexion with elec- 

 tricity. They are of a chemical nature, and become inflamed on 

 coming in contact with the atmosphere, owing to the nature of their 

 constitution. 



I think it highly probable that the fires that sometimes break out 

 in forests are caused by these lights. 



Art. XL. — Observations on the Influence of Locality, Time 

 of Appearance, ^-c. on Species and Varieties of Butterflies. 

 By. J. C. Dale, Esq. M.A. F.L.S., &c. 



Papilio Machaon, though an abundant insect in some places, 

 varies but httle except in size ; it has not been seen at Glan- 

 ville's Wootton since the year 1818. 



Colias Hyale has occasionally a white female, and also a 

 variety with the black border broader. C. Edusa varies very 

 much in size and colour, the variety of the female which 



