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posed hypothesis ? But might it not have been only the thin and 

 wasted remains of a dead fly, the transparency of which has been 

 increased by its becoming filled by the bright and clear bitumen ? 



Having hazarded the conjecture that amber has existed, as a 

 bitumen in a fluid state, and that the foreign substances it contains 

 were introduced in it whilst it was in that state, it may be expected 

 that some instances should be adduced of its having been found in 

 an intermediate state between that of fluidity and that in which 

 it is supposed constantly to exist. 



But it must be considered that the characteristic physical pro- 

 perties of amber, such as yielding a peculiar odour, and becoming 

 attractive by friction, depend on its indurated state, and must 

 therefore be sought for in vain, in an inferior state of inspissation. 

 To ascertain, with precision, therefore, from what species of liquid 

 bitumen it is derived, may be impossible ; since we are reduced, 

 whilst seeking for the analogous fluid bitumen, to trace it by the 

 aid only of such physical properties as colour, degree of trans- 

 parency, &c. which are common to both states. By these marks, 

 perhaps, if the substances had been examined with a view to that 

 inquiry, some analogy might have been discovered between amber 

 and those bituminous masses found by Stelluto, and those said to 

 resemble mastich and frankincense, which are described by Dr. 

 Woodward and Mons. Fontaine, and which were found even incor- 

 porated with fossil wood, with which substance, we have already 

 seen, amber is found generally associated. Were such specimens 

 again to be found, it would be, certainly, highly desirable to ascer- 

 tain whether, by continued exposure to a slightly increased degree 

 of temperature, or by long keeping, it would acquire the hardness 

 and other properties of amber. 



A specimen of elastic bitumen from Castleton, in Derbyshire, 

 which I possess through the kindness of Mr. Mawes, shows that 

 this variety of bitumen, in a soft state, may possess the colour as 



