Marsden — Temperature and Rainfall and Spread of Diseases. 49 



after deficient rainfall, and recede after rain ; and both spread more 

 actively after a series of dry years. 



How far does the resemblance between them go ? 



If we consider how constantly these two diseases are associated 

 together in the same individual ; and, again, how it not infrequently 

 happens that different persons in the same house, or even the same 

 family, will be attacked simultaneously — the one with scarlatina and 

 the other with diphtheria — does it not suggest the possibility that 

 these two diseases may be simply modifications of the same thing ? 

 Or, in other words, may they not be " allotropic forms" (to use a 

 chemical term) of the same disease, as charcoal and the diamond are 

 allotropic forms of carbon ? I think this may possibly be so. 



I am indebted to Mr. "W. E. Plummer, m.a., f.e.a.s., Director of 

 the Liverpool Observatory, Bidston Hill, Birkenhead, for the par- 

 ticulars respecting the weekly variations of temperature and rainfall 

 contained in the tables ; and to him I tender my best thanks for his 

 courtesy and trouble in the matter. 



