ASCENT OF MT. VESUVIUS 



in Phillips's Mineralogy. Calculated the dimensions and 

 angles of most crystals figured by him ; contrived a new 

 system of crystallographic symbols. Read attentively 

 Berzelius's article on chemical nomenclature. Thought 

 of some improvements. 



" In the course of March and April collected pupae of 

 the Hessian fly from the wheat-fields on the island of 

 Minorca, and obtained from them the perfect insect. 

 This, then, is no longer to be considered an American 

 insect. Afterwards found the same at Toulon and 

 Naples."* 



In July, 1834, he visited Mount Vesuvius, and wrote 

 a letter to his former teacher in New Haven, giving an 

 account of its condition. This was published in the 

 American Journal of Science in the following year, 

 the first of that long series of communications from his 

 pen by which that journal was enriched. 



At a later date, after his return, he speaks of arranging 

 on paper the results of his investigations of the geology 

 of Minorca, which considerably interested him while on 

 the island. 



By these tokens the coming naturalist is revealed ; all 

 this when he had but reached the age of twenty-one. 



To the rapid reader the Vesuvius letter may appear 

 somewhat dry, but those who are interested in the de- 

 velopment of Professor Dana's mind, and in his career 

 as an observer of geological phenomena, cannot fail to 

 notice that this ascent of Vesuvius made a strong im- 

 pression on the youthful student, and that he often 

 recurred to this experience in subsequent years, and es- 

 pecially in his study of the Hawaiian volcanoes. The 

 letter will therefore be printed in the second part of this 

 volume. 



* After returning from the Mediterranean, he published, in connection 

 with Mr. J. D. Whelpley, a description of two new species of Hydrachnella, 

 which are christened Hydrachna formosa and Hydrachna pyriforma, and, 

 in connection with Herrick, a detailed description of a new species of 

 Argulus^ which they named the Argulus catostomi, 



29 



