Woods and Wireless

Abstract

IN a letter in NATURE of April 7, Dr. Rolf makes some very interesting comments on the subject of absorption of wireless waves by trees, and refers to a paper in which I directed attention to this phenomenon. It is quite clear, as Dr. Rolf points out, that the capacity effect of the tree ought to be taken into account as well as its conductivity effect. It appears to me, however, to be a little doubtful whether such a simple modification of Sommerfeld's theory as Dr. Rolf proposes, is all that is required. The constants of conductivity and S.I.C. employed by Sommerfeld are for an isotropic medium, whereas used in connexion with trees they refer only to the vertical axis. Again, if we increase the conductivity of the tree we clearly increase the energy absorbed, and therefore the attenuation will be greater, whereas by Dr. Rolf's method, an increase of the conductivity leads to the opposite conclusion.