Mr. J. W. L. Glaisher on the Problem of the Eight Queens. 457 



some time, a strong solution of pyrogallic acid was introduced 

 through the separating-funnel into the bottle, and the tap of 

 the funnel was closed again. The gas thus freed from oxygen, 

 passed on through a calcium-chloride drying-tube into the 

 vacuum-tube which formed the upper part of a tube some 300 

 millims. long, the lower end of which just dipped below the 

 surface of mercury in a bottle, passing air-tight through the 

 cork. A second tube through the cork of this bottle put it in 

 communication with the air-pump. The vacuum-tube was thus 

 cut off by a sort of mercury-valve from the air-pump, so that it 

 was impossible for air to leak into the tube from the air-pump 

 during the process of exhaustion. Finally, one end of the 

 vacuum-tube contained sodium, and the other a minute frag- 

 ment of potassium chlorate wrapped up in platinum-foil. 



The gas having been allowed to pass briskly through the 

 apparatus for some time, the vacuum-tube was melted together 

 at the end remote from the air-pump, exhausted, and sealed off. 

 The sodium was then heated to ensure the absence of oxygen. 



The discharge from the induction-coil was then sent through 

 the tube. The light emitted (which was not very bright), exa- 

 mined with the spectroscope, gave the lines of the first carbon- 

 spectrum, the positions of the lines 5635 and 5165 being veri- 

 fied. The potassium chlorate was then heated so as to set free 

 oxygen, and the observations were repeated. The light was now 

 much brighter, and gave the second carbon-spectrum, the lines 

 5803, 5602, 5195, 4834, 4505, and 4395 being verified. We 

 have therefore only one spectrum which can be proved to be due 

 to carbon — that, namely, which is common to the flame of olefiant 

 gas or cyanogen, the electric discharge in cyanogen or carbonic 

 oxide at the ordinary pressure, and to the electric discharge in 

 vacuum-tubes enclosing cyanogen, olefiant gas, or hydrocarbons 

 such as benzol. 



LXI. On the Problem of the Eight Queens. 

 By J. W. L. Glaisher, M.A.* 



THE problem referred to in the title, viz. to determine the 

 number of ways in which eight queens can be placed on 

 a chessboard so that no one can take (or be taken by) any other, 

 was proposed by Nauck to Gauss, and formed the subject of a 

 correspondence between the latter and Schumacher. Gauss, after 

 finding the number to be 76 and then 72, ultimately arrived at 

 92, which has since been recognized as the correct solution. An 



* Communicated by the Author. 



