120 



Salt of hartshorn manifested no particular effect with the water 

 which first came over ; but with the bituminous liquor, allowed to 

 stand until it had become clear, it caused a considerable ebullition, 

 the mixture becoming foul and red ; and in a few days it became 

 thickened and of the colour of tar, the surface of it, as well as the 

 sides of the phial, being covered with a bituminous pellicle. By 

 exposing the black gritty powder, in a retort, to a red heat for two 

 hours, the neck of the retort became thinly incrustec 1 with something 

 that resembled a saline concrete, but which he found to be only a 

 bituminous matter. 



The black powdery residuum being kept red hot in a close vessel, 

 for a longer time than he thinks would be sufficient to have reduced 

 an equal quantity of vegetable charcoal, still emitted a thick heavy 

 smoke, when sprinkled on a red hot iron ; and upon farther expo- 

 sure to heat, in an open vessel, an astringent mineral salt was left, 

 but no other saline matter, which, he thinks, together with the bitu- 

 minous nature of its products, affords a sufficient proof of this fossil 

 wood differing from all known wood, belonging to the vegetable 

 kingdom, and of its being an actual mineral substance. 



I cannot close this letter without, in justice to Professor Hollman, 

 noticing the hard fate of his useful observations, or rather disco- 

 veries, on this subject. In the year 1753, he delivered to the Royal 

 Society of Gottingen, a most excellent dissertation on the origin of 

 marine, and other foreign substances, contained in the earth*; 

 which appeared in the third volume of the Society's Transactions. 

 Another dissertation, the one from which we have derived so much 

 information -f-, was also decreed to appear in the fifth volume of the 

 same work ; but foreseeing, what actually happened, that the lat- 

 ter paper would be excluded from public view, in consequence of 



* De Corporum marinorum, aliorumque peregrinorum, in Terra continente, Origine. 

 t Loci memorabilis, in quo ingens Ligni fossilis Copia reperitur, Descriptio. 



