104 ALEXANDER VON HUMBOLDT. 



The following is from the letter to Sommering of January 

 28, 1791, from which extracts have been already given: 



' I had written thus far about three weeks ago, and have since 

 been prevented by illness from finishing my letter. 



6 To-day I am going to add to this already lengthy epistle a, 

 drawing of what has been called a petrified child's hand, which 

 was found in the slate beds at Riegelsdorf. The phalanges 

 show clearly enough that it is the paw of an animal, and could 

 never have formed part of any human being. Perhaps you 

 may be better able to determine its classification ; is it likely to- 

 be a species of otter ? Such a thing is not altogether impro- 

 bable, for thirty fathoms below the surface at Riegelsdorf there 

 is an extensive bed of limestone, considerably contorted, contain- 

 ing fossil fish. Pray assure Forster of my heartfelt esteem, and 

 tell him that I have frequently repeated his experiment of the 

 phosphorescence of potatoes with great success. If, in connec- 

 tion with Fourcroy's discovery of the existence of albumen in 

 many plants, we call to mind the fact that animal lime is con- 

 tained in the cereals, and volatile alkali l in the tetradynamia 

 the luminosity seen in potatoes is also to be observed in beef 

 and salmon we shall begin to see something of the affinity 

 between animal and vegetable life. Yet another question, my 

 dear friend. Where could I meet with some comprehensive 

 treatise on the formation of animal bone? which, though really 

 composed of limestone, is impregnated with phosphoric acid, 

 and constitutes that which Werner has designated uncrystallised 

 phosphate of lime. I am at a loss to know how the calcareous 

 earth can be evolved from the slight nourishment taken by 

 ,an infant.' 



There are still extant some letters written about this date to 

 Dr. Grirtaner, whose acquaintance Humboldt made in London. 

 The subject of one of these letters is an unpleasant misunder- 

 standing with Usteri, the editor of the ' Magazin fur Botanik ;' 

 while in another letter Humboldt mentions that he was to leave 

 Hamburg at the end of April, and proposed to spend a fort- 

 night at Berlin with his mother and ' excellent ' brother, on 

 his way to Freiberg, where it had been arranged that he should 

 pass the summer. 



1 [An old name of ammonia.] 



