in Recent as well as in Fossil Bones. 291 



The glass was allowed to remain as a cover to the platina crucible 

 for at least two hours, and in order to insure the condensation upon 

 it of the hydrofluoric vapour, a rim of wax was placed round the 

 margin of the upper surface of the glass, by means of which a small 

 portion of water might be kept the whole time in contact with it, 

 so as to maintain a suitably low temperature. 



That these precautions were not unnecessary, I satisfied myself 

 by observing the difference in the degree of corrosion produced by a 

 fossil bone given mo by Dr Buckland from the cave of Kirkdale in 

 Yorkshire, when thus purified from the animal matter by which its 

 loiig interment had not yet deprived it, as well as of its carbonic 

 acid, as compared with the same when treated with sulphuric acid 

 without having undergone such a preparation. 



In proof of this I submit to the inspection of members, specimens 

 No. 3, and No. 4 ; the one shewing the glass corroded by a Kirk- 

 dale bone, deprived of its animal matter and carbonic acid ; the lat- 

 ter, by one retaining both. Operating in this manner, I have suc- 

 ceeded in engraving upon glass, not only by means of fossil bones 

 from Stonesfield, from Montmartre, from the cave of Kirkdale in 

 Yorkshire, and from that of Gailenreuth in Franconia, specimens of 

 all which were supplied me by Dr Buckland ; but likewise with the 

 bone of some quadruped that had been lying for a long, but unknown 

 time, exposed to the weather in the soil of our Botanic Garden ; 

 with the vertebra of an ox recently killed ; with the tibia of a human 

 subject from an anatomical cabinet at Oxford ; with the teeth of an 

 ox just killed ; and with human teeth of recent date. The markings 

 differ widely in the degree of their distinctness, and are, in some 

 instances, so faint as hardly to be discerned except by day-light ; but 

 I have convinced myself, that they cannot be attributed to the dis- 

 engagement of phosphoric acid, as the same glass was in no degree 

 affected by the fumes proceeding from the action of sulphuric acid 

 upon pure phosphate of lime, where the acid had been derived from 

 the direct combustion of phosphorous, nor, for a long time at least, 

 by the vapour of free phosphoric acid exposed to a heat sufficiently 

 great to fuse and partially to volatilize it. 



Nor was it dependent on any peculiarity in the nature of the 

 glass, for plate glass was corroded in the same manner as the crown 

 glass, more usually employed. 



By the oldest and most fossilized specimens, the glass seemed 

 undoubtedly to be the most deeply etched ; yet even here there 

 occurred exceptions, for the marks caused by a bear's bone taken 

 from Gailenreuth, are the faintest in the whole series, and were 

 produced only after a long exposure to the acid vapours, two trials 

 having proved unsuccessful ; whilst, on the other hand, the tibia of a 

 human subject gave indications almost as distinct as any of the 

 fossil bones operated upon. 



It would doubtless have been more satisfactory if I could have 



