M. Boussingault on the Composition of Bitumens. 77 



This voyage afforded me an opportunity of making many new 

 and very important observations, in correcting the map of this 

 great island, and completing that of the Archipelago on the 

 north-east, at which I had worked for so long a time. 



The map of the Isle of France which I drew up with much 

 care, and the accuracy of which I can vouch for, was engraved 

 in England, by order of the Quarter-Master-General. I sent 

 it to the depot at Paris, but it appears that it was intercepted 

 on the voyage in 1808. 



On the Composition of Bitumens. By M. BOUSSINGAULT. 



THE bitumens which are so abundantly spread over the face 

 of the globe, and whose uses are every day becoming more varied 

 and extensive, have hitherto been little examined. If we except 

 the labours of M. de Saussure upon the naphtha of Amiano, we 

 are nearly in complete ignorance concerning the intimate nature 

 of these bituminous compounds. 



It is to this insufficiency of the data supplied by chemistry 

 that we must attribute the confusion into which most mineralo- 

 gists have fallen in theirattemptsto classify the different bitumens. 

 A systematic place can easily be assigned to naphtha, idrialine, 

 and mellilite or honey-stone, but when we come to petroleum we 

 get involved in difficulties ; this substance usually met with in a 

 liquid state, now becomes viscid, and successively presents all 

 possible degrees of consistence, till we arrive at asphaltum, which 

 is solid and brittle. We are generally led to admit that the bi- 

 tumens owe their fluidity to naphtha ; but the results of the pre- 

 sent investigation shew that there is no ground for this supposi- 

 tion. The attention of the author was first directed to the viscid 

 bitumen of the Departement du Bas-Rhin. After describing the 

 method in which the bituminous sand is treated, he gives a ra- 

 pid sketch of the locality of bitumens ; and shews that the im- 

 mense masses of mineral pitch which are found on the banks 

 of the River Magdalena, at Payta, upon the coast of Peru, 

 have a geological position precisely similar to that in which we 

 find bituminous impregnated sands in Europe ; that is to say, 

 in formations which we must refer to the supercretaceous group. 



