370 Messrs. Walker and Hatton on the Determination of 



melting-point phosphorus, while curve (4) shows the rale 

 of cooling of the other variety : both these curves are for the 

 cooling of equal quantities of phosphorus. It will be seen 

 that there is an appreciable difference in the heat given out ; 

 and this too is to a great extent masked, as the rhombic modifi- 

 cation, on solidifying without cooling previously to below its 

 solidification-point, is converted to a great extent into the 

 octahedral modification. This is also the reason why both 

 modifications solidify at the same temperature, viz. 43°* 8. 

 This temperature may therefore be taken as the solidifying- 

 point of the octahedral modification, while that of the other 

 variety is not known. It must, however, be a temperature 

 below and not above this point. In order to determine it 

 accurately, it would be necessary to cool a very large quantity 

 of liquid phosphorus to below this temperature and then cause 

 it to solidify, and notice the temperature to which the ther- 

 mometer rushed up. If only a moderate quantity of phos- 

 phorus, as fifty grams, were thus treated, the heat of solidifi- 

 cation would not be sufficient to raise the temperature of the 

 mass up to the true temperature of solidification. 



The different properties of the two modifications of phos- 

 phorus may be summed up as follows : — 



Octahedral modification. 



Has definite melting-point at 

 44°-3. 



Specific gravity at 13°, 1-8177. 



Has considerably greater latent 

 heat of fusion than rhombic 

 variety. 



Formed from the rhombic va- 

 riety bv cooling rapidly. 



Solidifies at 43°-8. 



The University Laboratory, 

 Oxford. 



Rhombic modification. 



Has no well-defined melting- 

 point : melts at about 45 0, 3. 



Specific gravity at 13°, 1-8272. 



Has less latent heat of fusion 

 than octahedral variety, and it 

 begins to absorb this at about 38°. 



Formed from the octahedral 

 variety by cooling slowly, so 

 that it cools below the solidifi- 

 cation-point before solidification 

 sets in. 



XLYII. Experimental Determination of the Beats in the Vibra- 

 tions of a Revolving Bell. By James Walkeb, M.A., and 

 J. L. S. Hatton, B.A., Demonstrators at the Clarendon 

 Laboratory, Oxford *. 



IN a communication read before the British Association 

 at Leeds, and in a paper published in the Proceedings 

 of the Cambridge Philosophical Society (vol. vii. p. 101) 



* Communicated by the Authors. 



