WEBER'S LECTURES 63 37. H. F. Weber's Lectures on Physics [ca. December 1897-ca. June 1898][1] Vorlesungen über Physik von Weber. Für eine auf die Temperatur T erhitzte Kugel von homogenem Material, deren Oberfläche von der Zeit z = 0 an konstant auf der Temperatur t = 0 gehalten wird, wurde als Gesetz der Tempera- turverteilung gefunden:[2] ADS. This document is written in two bound notebooks. The first, 17.5 x 21.5 cm, consists of lined white paper. Each page is folded to create an outer margin of 5 cm. The second, 17 x 21.5 cm, contains squared white paper. A left margin of three to five squares is main- tained on each page. A number of pages toward the end of this notebook have been cut out. The manuscript is written in ink, with occa- sional additions and changes in pencil or in another ink. Such emendations are indicated in footnotes. Marginal notes in the original are printed at the corresponding place in the margin diagrams from the original are usually placed within the printed text. Some calculations written on the inside back cover of the second notebook are printed in note 197. Three pages of research notes, dated to a later period, will be printed in Vol- ume 2. Thirteen pages of unrelated notes on mathematics, written at the end of the second notebook, and a loose sheet of unrelated notes enclosed in the first notebook, are omitted. [1] Einstein's notes are dated on the basis of the assumption that they start with material discussed about the middle of the winter se- mester of 1897-1898, and end with material discussed about one month before the end of the summer semester of 1898. This assumption is suggested by a comparison of Einstein's notes with Teucher's (see editorial note, "Einstein as a Student of Physics and His Notes on H. F. Weber's Course"). [2] Teucher's notes indicate that, earlier in the course, Weber had derived the following solution to Fourier's heat conduction equa- tion. The initial temperature T is now denoted by t0 c, p, and R denote the specific heat, density, and radius of the sphere, respectively, and r is the radial distance from its center. The heat conductivity K is defined through the equation dW = K f(-dt/dn)dz. f is the area through which the quantity of heat dW passes during the time interval dz, and dt/dn is the gradient of the temperature t in the direction normal to f. lirr 2RSffl R 1V2K e Tk~pcz it r 2irr 2R Sifl R 4ir2 __ 2 r R2 3irr 2R R 9ir2 K +to e r2 - r2