3 8 I^RINCIPLES OF GENERAL PHYSIOLOGY 



taught in our schools, as is well pointed out by Prof. Perry in his "Calculus for 

 Engineers." 



As a brief introduction, the first chapter of Melloi's "Chemical Statics and Dynamics" 

 may be recommended. The admirable book of Nernst and Schunflies, of which unfortunately 



FIG. 25. RENE DESCARTES. 



(From the portrait by Franz Hals, in the Louvre Gallery. 



no English translation exists, may follow, and then, perhaps, Mellor's " Higher Mathematics 

 for Students of Chemistry and Physics." 



Experimental results can almost invariably be best expressed graphically, owing to the 

 direct appeal to the eye. 



The way in which algebraical foimuhe can be represented by geometrical figures, or vice 

 versa, was discovered by Descartes and published in his famous "Geometric" in 1637. The 

 co-ordinates when referred to two axes at n angle to one another, are accordingly known as 

 "Cartesian co-ordinates." This system, with the axes at right angles, is that most commonly 



