614 Mr. T. T. Wilkinson on Mathematics and Mathematicians : 



Its composition therefore, with the exception of a slight defi- 

 ciency in the amount of hydrogen, was that of verantine. 



The acid hquid filtered from the substance was evaporated 

 almost to dryness, when it yielded a quantity of yellow crystals. 

 These were washed with cold water, and then redissolved in a 

 little boiling water. The boiling solution was decolorized with 

 animal charcoal, and after being filtered boiling hot deposited 

 on cooling a quantity of colourless crystals, having the appearance, 

 find as their analysis showed, the composition of Laurent's naph- 

 thalic acid. 



0*5230 grm. gave 1*1020 carbonic acid and 0*1770 water. 



In 100 parts— 



Naphthalic acid. 

 Carbon .... 57-46 57*83 



Hydrogen . . . 3-76 3*61 



Oxygen .... 38*78 38*56 



Wolff and Strecker mention, that purpurine yields this acid 

 when subjected to the action of nitric acid, but the verantine 

 which is found in an undecomposed state, after the action of the 

 nitric acid has ceased, seems to have eluded their observation. 



From these experiments I infer that purpurine, madder-purple, 

 and the various similar bodies derived from madder, owe their 

 property as colouring matters to an admixture of alizarine, and 

 that they simply consist of the latter substance in a state of im- 

 purity. 



LXXX. Mathematics and Mathematicians. The Journals of the 

 late Reuben Burrow. By T. T. Wilkinson, Esq., F.R.A.S., 

 and Corresponding Member of the Manchester Literary and 

 Philosophical Society. 



[Continued from p. 193.] 

 No. II. 



SINCE the preceding article of this series was written, the in- 

 defatigable Astronomer Royal has communicated a paper 

 to the Royal Society which sets at rest the occurrence of an 

 eclipse when Xei-xes was setting out from Sai-des on his expedi- 

 tion to Greece (Phil. Mag. March 1853, pp. 216-218). 



" The author thinks it most likely that the phsenomenon 

 really was the total eclipse of the moon which occurred on the 

 morning of March 14, b.c. 479 ; *' but Mr. Burrow appears to 

 have been led to the conclusion that an eclipse of the sun must 

 have taken place about the same period, as is evident from a 

 memorandum which I have since met with, as follows, in an ob- 

 scure corner of some disfigured leaves at the end of the Journal. 



" In the year 478 before Christ. 



