i903.| GOODSPEED—FIELD SURROUNDING CROOKES TUBE. 103 
The inference seems fair that the recurrence of the inflammatory 
condition was not a mere coincidence, and that these secondary 
rays may be found to be of more importance than has been sup- 
posed. 
BIBLIOGRAPHY. 
1 Thompson, X-Rays, p. 70. 
2 Thompson, X-Rays, p. 129. 
3’ Sagnac, Compte Rendus, 1897-98. Sagnac, Annales de Chemie et de 
Physique (7), xxii, 1901; pp. 493-563. Perrin, Comte Kendus, Vol. cxxiv, 
p- 455. Townsend, J. S., Proc. Camb. Philos, Soc., 1900, x, pp. 217-226. 
4 Guilloz, Compte Rendus, February, 1900. 
UNIVERSITY OF PENNSYLVANIA, 
RANDAL MORGAN LABORATORY OF PHYSICS, 
May 15, 1903. 
