174 
metrical pressure, though by using Regnault’s or Apjohn’s 
original formula the difference is not so very great. 
I have, however, noticed that in some papers on high 
climates presented to the London Meteorological Society, 
Glaisher’s tables have been used without applying any baro- 
metrical correction, whereas the tables are arranged for 
England, and not for a barometrical pressure of 25 inches 
without correction. 
In Dr. C. Theodore Williams’ communication “On the 
Winter climate of Davos,” Meteor. Journ he seems to have 
taken the mean of the month’s temperature of the wet and 
dry bulb,* and then by the aid of Glaisher’s tables without 
barometrical correction, put down the “ relative humidity” 
obtained from these figures as the month’s mean, causing in 
many cases a very considerable error. For instance, he 
gives Jan., 1881, from mean temperature of air at 1 p.m. 
28‘9° F., mean of evaporation 24*6° F., the relative moisture 
as 40, to which he refers in the text as showing how dry 
the month was, whereas if he will calculate this out by 
Apjohn’s formula 
^ d h 
96 X 30* 
he will obtain COT, though if he had taken the mean of 
each day’s humidity he would have obtained about 67'0 re- 
lative humidity.^ It is very unfortunate that anyone of 
Dr. Williams’ medical reputation, and who has written 
several important things on Davos, should have given his 
name to a paper where the observations are open to grave 
doubts, and the calculations made as if Davos was on the 
sea coast. 
I have, however, found that the moisture as calculated 
* These figures cannot give the mean humidity correctly, but it 
must be calculated out for each day, and then the mean of these results 
given. 
f Mr. Muddock’s figures of observations taken by the same observers 
give for Feb., 1880, temperature at 1 p.m. 36 '06° F., not 38‘4 as given by 
Dr. W. 
