CORRECTIONS. 



P. 144. —For Plates 1, 2, and 3, read Plates XXII., XXIII., 

 and XXIV. — It should also be noted that plates I. - 

 XXIV. replace numbered pages of text. 



163, several places. — For Crotallaria read Crotalaria. 



171, second line from bottom. — For Anthremus, read An- 

 threnus. 



201, first line. — For constructions, read properties. 



202, first four equations. — For 2, read 4. 

 214, fifth line. — For least, read greatest. 

 224-8. — For s, read 2. 



241, sixth line from bottom. — Yovfilamenta, read filij 'era. 



3 



293, equation 43.— For wy ~ " ° ^ + y ^ 



mx 3 



read ™V ~ * ™ (** + V*)\ 



mx 

 427, line 8. — For Schradophylluin Jacquinii read Sciadophyl- 

 lum Jacquini. 



Concerning No. 12, Mr. Roever submits the following note: — 



After the introduction of the electrified point or the electrified line into 

 a field of electric force which before the introduction of the electrified point 

 or the electrified line is uniform in direction and magnitude at every point 

 (and may be the field of an isolated electrified plane of infinite extent) the 

 equipotential surfaces cease to be planes (except at an infinite distance). 

 Owing to this fact the following wording should be substituted for that on 

 the title page: — 



Geometrical properties of the lines of force proceeding from 



(a) A system consisting of an electrified straight line surrounded 

 by a field of electric force which before the introduction of 

 the electrified line was uniform in direction and magnitude at 

 every point. The electrified line is perpendicular to the 

 direction of the force in the original field. 



(b) A system consisting of an electrified point surrounded by a 

 field of electric force which before the introduction of the 

 electrified point was uniform in direction and magnitude at 

 every point. 



The wording on pages 273 and 285 (printed in italics) and in several other 

 places should also be changed. The reader will, however, receive a cor- 

 rect impression from the uncorrected statements by thinking of a field of 

 electric force which is uniform in direction and magnitude at every point 

 whenever " electrified plane " is mentioned. He will also think of the magni- 

 tude of the field force as being represented by F instead of by 2~ a. 



Notwithstanding these corrections, the mathematical results reached are 

 correct. 



