272 PHILOSOPHICAL TRANSACTIONS. [aNNO \6q9- 



ing it were, as in the former experiments, a burning in the flesh, and shortness 

 of breath ; they all went off, and in 5 days time she seemed perfectly recovered. 

 Thus we see a quantity of ibiiji of warm water has been injected into the 

 middle venter of the same greyhound within the space of one month ; and if 

 we may be allowed to judge of the recovery, by a perfect cessation of all symp- 

 toms as to outward appearance, we must then grant, that this water was carried 

 off thence in the time. But to give an account which way it was discharged, 

 whether by expiration, perspiration, stool, or urine, seems very difficult, and 

 is beyond my anatomy to explain ; only thus much I must say, as to the latter, 

 that having ordered the greyhound to be tied up, after one of the last two ex- 

 periments, within two or three days, I observed the boards of the floor where 

 she lay to be very wet, which I then imagined to be the effects of the injection 

 come off by urine. If I may conjecture in so uncertain a matter it is, that as 

 nature has furnished us with vessels to bring off that humour which is thrown 

 into the ventricles of the brain, which by tarrying there would prove fatal to 

 us, so likewise possibly there may be some ductus yet unknown, which, belong- 

 ing to the thorax, may convey off thence what liquor arises, either from the 

 condensation of vapours, or from the rupture of lymphatics, or any other way, 

 in the cavity, mediately or immediately into the blood; certainly these experi- 

 ments, as also the many histories of empyemas and dropsies of the breast, men- 

 tioned by physicians, as cured by large evacuations by urine, do, in some mea- 

 sure, argue the possibility of this thing ; but whether there really be any such 

 passage may shortly be determined by further anatomical experiments.* 



Observations on the Substance commonly called Black Lead. By the late Dr. 

 Robert Plot, F.R.S. N° 240, p. 183. 



The mineral substance, called black lead, found only at Keswick in Cumber- 

 land, and there called wadt, or kellow, by Dr. Merret, nigrica fabrilis, is cer- 

 tainly so far from having any thing of metal in it,-|- that it has nothing of fusion, 

 much less ductility ; nor can it be reckoned among the stones, for want of hard- 

 ness; it remains therefore that it be classed among the earths, though it dissolve 

 not in water, as most earths will, except stiff clays and ochres, among the 



* The water in these experiments would be taken up by the absorbents with which the pleura, 

 investing the cavity of the thorax, is furnished ; and after entering the circulation would be carried 

 to the kidneys ; where it would be separated from the sanguineous mass, and descending to the blad- 

 der would by its outlet the urethra, be discharged from the body. 



+ This is erroneous. It has been shown by the analyses of modern chemists that this mineral 

 substance contains a portion of iron, though its chief constituent part is carbon. It is the plumbago 

 of Kirwan, the Graphit of Werner, and the carburetted iron of the new chemical nomenclature. 



