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having left or nearly left the valleys. The late Mr. Weston of 
Ensleigh, who made his meteorological observations at the same 
hour, 9 a.m., as those made in the Institution Gardens, once 
remarked to me how different at that hour it frequently was with 
him at his elevation of 740 feet above the sea from what it was 
lower down, the dry-and wet-bulb thermometer indicating satura- 
tion, when at the Institution there might be a difference between 
the two bulbs of that instrument of one, two or more degrees. 
In the case of persistent fog through the day, the reverse of 
this take place, the thick air becoming clearer as we ascend higher. 
It was a common occurrence, when I lived at Swainswick and 
walked into Bath in such weather, to find the fog getting thicker 
and thicker as I approached the town, and sometimes in the town 
itself passing into actual rain, the rain falling fastest in the lower 
part of the town near the river,—when at Swainswick perhaps 
there was little or no rain the whole day. 
The fogs above spoken of are most frequent in Bath in the 
autumn and winter months, when the temperature is low and the 
relative humidity of the air is at its maximum. They occur, 
however, at other seasons occasionally, when the atmospheric 
conditions are favourable for their formation. 
I was desirous of ascertaining from the Institution Registers the 
relative frequency of these fogs in the different months, but as 
they have not been entered in the Registers in all cases, I have 
confined myself to marking down the mean number of days in 
each month on which the dry-and wet-bulb thermometers have 
been coincident, or within one degree of coincidence, at 9 a.m. the 
hour of observation. Perhaps there is more of interest and utility 
in such a return than there would be in a return of the mere fogs 
themselves, as it indicates very exactly that state of humidity, 
which so far as I have noted is almost always either accompanied 
by fog, or if no fog by rain, more or less, and so speaks more 
directly to the character of the climate in this respect. 
Also, as the fogs in Bath are mainly due to the river in connec- 
