iv EDITOR'S PREFACE. 



remains, which, for the present, is beyond our reach, and which may for- 

 ever remain so. However this may be, the facts established in this and 

 in the preceding work of the Author have very materially extended the 

 application of the well-known laws of physics and of chemistry to physio- 

 logy, and have also furnished a number of the most beautiful instances of 

 that infinitely wise, but exquisitely simple adaptation of means to ends, 

 which characterizes all the works of the omnipotent Creator ; but which is 

 no where more admirably displayed, than in the arrangements, imperfectly 

 known as they hitherto are, by which life is maintained. 



In connection with the Author's remarks on the effects of evaporation 

 in plants, and the consequences of its suppression, and with his opinions 

 as to the origin of the potato disease, I beg to refer the reader to the 

 Appendix for a very ingenious and apparently well founded plan for the 

 protection of the potato plant against the terrible scourge under which it 

 has lately suffered. The views of Dr. Klotzsch, the author of this plan, 

 as to the nature of the disease, coincide remarkably with those of Baron 

 Liebig, as explained in the present work. 



WILLIAM GREGORY. 



EDINBURGH, 3d March, 1852. 



