CONTRIBUTIONS TO SCIENCE. 575 



Thermodynamic Surface. This surface, in which the co- 

 ordinates represent respectively the energy, entropy, and 

 volume of the substance to which it corresponds, was 

 modelled in clay by Maxwell's own hands in the Cavendish 

 Laboratory. From the clay model a number of plaster 

 casts were taken. These casts Maxwell placed in the sun- 

 shine in particular positions, and drew upon them in water- 

 colours the boundary-lines between the light and shadow, 

 which correspond to constant pressure or constant tempera- 

 ture, on the part of the substance. An account of this 

 surface, and many of the properties which it represents, 

 will be found in the work referred to. 



We have now presented to the reader a scanty selec- 

 tion from the results of Maxwell's scientific work. The 

 mere enumeration of his original papers would occupy 

 several pages of this book, and those who are desirous of 

 forming any approach to a true conception of his contribu- 

 tions to science should consult the memorial edition of 

 Maxwell's papers, edited by Mr. W. D. Mven, F.E.S., and 

 about to be published by the Cambridge University press. 



END OF PAET II. 



