14 Dr. Troost oil Amber, iSfii. 



2d. Does this insect make its nidus of resinous matter^ aj* llie 

 coccus lacca? 



3d. \¥hat species of trees do tiiese insects inhabit ? 



Note Sccotuly p. 10. — Nature seems to have adopted this bed of 

 lignite as its laboratory for the formation of sulphur, of which the 

 pyrites are composed — at least, it is true, that above this bed not 

 the least vestige of this mineral is to be found, whereas, it appears 

 as soon as the lignite is discovered. In the superior part, the py- 

 rites is found in the wood partly charred ; lower down is found, here 

 and there, the sand which exists in the interstices of the wood, 

 agglutinated by pyrites, and at other times, uniform pieces, or 

 twigs of trees entirely changed into this mineral, the cavities lined 

 with small crystals. Beneath this bed, in the stratum of sand, of 

 which we have made mention in this memoir, are large masses of 

 pyrites, found principally in the inferior part of the stratum, at a 

 spot where the water has been prevented from infilterihg itself to 

 a lower depth, by the bed of earthy lignite through which (as in the 

 rase of common clay) water does not penetiate but with great diffi- 

 culty, if at ail. In the stratum of earthy lignite, tlie greatest part of 

 these branches have been changed into pyrites, and have preserved 

 the primitive structure of wood ; in the stratum of sandstone which 

 serves as a support to the lignite, we find small masses of sand ce- 

 mented together by pyrites. This stratum is generally ten or twelve 

 feet below the surface of Magothy river, and of course, that which 

 filtered through the superior strata, descends no lower than in a 

 proportion to its greater density compared with common water, 

 which density it has acquired, in its passage, by the solution of for- 

 eign matter. Below this bed, of which the mean thickiiess is three 

 feet, no pyrites are formed. 



What shall we conclude from ail this ? Here I would hazard 

 my opinion. Let us at first suppose that the constituent parts of 

 the sulphur are lodged in the vegetable matter — that only an active 

 agent is wanting to disengage them from the matter with which 

 they are combined, and to recombine them to produce sulphur — 

 let us suppose, at the same time, this agent to be water, or water 

 charged with iron, then the water, by filtering through the superior 

 stratum, which, as has been said, is sand agglutinated by oxide ol 

 iron, is charged with the iron, and meeting in the stratum of lignite 

 the constituent parts of the sulphur, has put the same into action. 

 The sulphur being, now made,* has entered into combination with 

 the iron, producing for result, the pyritous matter, partly filling, in 

 the first place, the cavities occasioned by a decomposition in the 

 wood, by which Oj)eration the pyrites has acquired the form and 

 the very texture of the wood. The liquid thus generated, filtering 



^ Doe? Dr. Troost -joiisiiler SL!l[!hur as a coinpound .' Ed. 



