Sir Robert Robertson 203 



tax. Here again the cameras and rays of the Laboratory 

 have been used to show up the erased figures. However 

 carefully they may be rubbed out, they come up clearly 

 in these interesting photographs. 



Again, by the use of chemicals unscrupulous people 

 have been able to delete the markings on used unemploy- 

 ment stamps, and so to use them over again. Yet once 

 more Science has proved too clever for the swindler, who 

 has found himself heavily fined for his efforts to get the 

 better of the State. 



At the Record Office in Chancery Lane there is the 

 most wonderful collection of ancient documents in exist- 

 ence, and not the least interesting is Shakespeare's 

 marriage settlement. Not long ago the staff at the 

 Record Office were shocked to discover a blot of ink on 

 Shakespeare's signature. No one remembered having 

 seen this before, and there was doubt as to whether it 

 was an old blot or a new one. Off went the document to 

 the Laboratory, and almost at once came the answer that 

 it was a new blot. A test of the ink proved it to be made 

 from aniline dye, which of course did not exist in Shake- 

 speare's time. The blot was removed and the document 

 returned to the Record Office. 



The great increase in the use of gas and electric light 

 has reduced the number of oil lamps used for lighting 

 purposes, but on the other hand there has been a very 

 great increase in the sale of oil-burning lamps for cooking 

 and heating. Oil used in these lamps must not ' flash ' 

 — that is, give off inflammable vapour in a closed vessel — 

 at a temperature below one hundred degrees Fahrenheit. 

 Many samples of oil are tested yearly in the Laboratory 

 to make sure that they comply with the law. What is 

 called the Ableclose test is used for this purpose, and all 

 kinds of oil are tested, including samples of oils used in 

 lighthouse lamps, sent by Trinity House. 



' Fire-bugs ' — as they call them in America — have been 



