IS 14.] accelerating the Progress of Mineralogy. 129 



I will now finish this explanation of my ideas respecting the 

 classification and nomenclature of minerals. I hope it will not 

 he entirely unworthy of your attention, as it is the result of 

 experience. I entreat you, Gentlemen, to consider this memoir, 

 or rather this dissertation, as an introduction to several memoirs 

 which I will take the liberty of presenting to you. My travels 

 and my collection furnish observations which may be interesting 

 to the mineralogist and the geognost. Allow me to recall to 

 your recollection a well-known maxim, the truth of which is 

 daily confirmed by your example, Modesty is the signet of great 

 talents. Werner is the only person who gives the name of 

 arktizite to a substance to which, out of gratitude, the name of 

 Wernerite has been given. Haiiy is the only person who has 

 preserved the name of latiolite to the substance to which 1 gave 

 the name of Haityne, to recall to posterity the name of a man 

 to whom the sciences have so many obligations. 



Article IX. 

 On the Arctia Phceorrhcea. By Thomas Thomson, M.D. F.R,S>. 



In my walks in the neighbourhood of Chelsea this summer I was 

 much struck with the appearance of the hawthorn hedges. A con- 

 siderable portion of them was quite withered, as if they had been 

 exposed to a sudden and intense frost. These withered patches 

 sometimes extended for a hundred yards in length ; then came a 

 green portion, which was in its turn succeeded by another withered 

 tract, and so on. The withered parts appeared quite covered with 

 webs similar to that of the spider; and, upon a closer inspection^ 

 prodigious numbers of a black spotted caterpillar were seen enve- 

 loped in the webs, or hanging from them. During the month of 

 May it was easy to find thousands of these animals devouring the 

 leaves of the hawthorn. It was to their voracity that the withered 

 state of the hedges was owing; for the whole leaves being destroyed, 

 the plant ceased to grow, and assumed a wiutery appearance. I 

 irved this insect likewise upon elm-trees, and upon apple-trees ; 

 but not on beech, holly, yew. or privet, which were almost all 

 the trees or shrubs that I observed in the hedges round about 

 Chel 



The prodigious ravages committed by this insect induced me to 

 make some inquiry respecting it ; and though the facts which were 

 Stated to me have been long known to entomologists, yet I have 

 thought them important enough to deserve notice in the Annals of 

 Philosophy, as thev may be of some utility to the fanner or gar- 

 <h u< t, and it- thrv can scarcely fail to be an object of curiositv to 

 •vei") who has noticed the ravages of this destructive insect. 



i IV. N° II. 1 



