354 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1954 



in bony carbonate-apatites, gradually replaces the phosphoric acid of 

 the phosphates. Finally, our knowledge of isotopes has very recently 

 made an extremely useful contribution to the study of fossilization by 

 means of the quantity of the radioactive carbon isotope (Cn) in the 

 carbonates of the bones. During life, the proportion of radioactive 

 carbon in the bones (as, incidentally, in plants) is the same as in the 

 carbon dioxide in the atmosphere. After death, and when the body 

 is buried in the ground, this radioactive carbon spontaneously disinte- 

 grates, half of it disappearing in about 5,600 years. By determining 

 the remaining radioactivity of a fossil bone, therefore, we can date it 

 with a very close approximation to accuracy. The amount of Ci4 in 

 the wood of the funeral barge of Sesostris, for instance, which was 

 thought to be 3,792 years old (to within 50 years either way), made it 

 possible to establish that the barge was approximately 3,700 years old. 



When a tiny fragment of paint from a broken door is found on a 

 burglar's jimmy, we have, if we are to establish definitely that the 

 jimmy in question was actually in contact with the door it was used 

 to break open, to make a comparative analysis of the scrap of paint 

 on the jimmy and the paint on the door. Microscopic examination is 

 of no use in this case, the only valid proof being the identification of 

 the paint's ingredients. Unfortunately, the qualitative composition 

 of most ordinary paints is very similar. Quantitative analysis is there- 

 fore necessary, sometimes on a sample weighing only a few tenths of 

 a milligram. Spectrography is the only possible means we can use, 

 and even that must be conducted under very strict control. 



The expert examination of works of art is much in the public eye. 

 Police laboratories are more and more often consulted during judicial 

 inquiries to establish whether or not such works are genuine. The 

 increasing number of forgeries, the skill with which they are made, 

 and the threat they constitute to our artistic heritage, necessitate the 

 use of more and more complicated techniques for their detection. 



It is exceedingly difficult to give an expert opinion on a piece of 

 furniture. There may be, for instance, a Louis XV bureau with 

 carved bronze ornaments, which is apparently of very great value. 

 How can we establish whether or not it is faked? Analysis of the 

 bronze ornaments shows that they are gilded by the mercury process 

 commonly used in the eighteenth century, and so worked that the piece 

 cannot possibly be a modern copy. Examination of the wood estab- 

 lishes that it is old and also dates from about the same period; certain 

 later sections have been given an artificial patina. But this wood had 

 already been used before being incorporated in the bureau, and was 

 cut to fit the latter by means of a power saw. The piece is therefore 

 a copy but an old copy, probably dating from the First Empire. 



Or we may have a large glazed terracotta panel, attributed to 

 Andrea della Robbia ; if it is genuine it is a real museum piece. Expert 



