Natural Philosophy. — -Meteorology. 189 
that of a sharp frosty morning in England. In an account of 
Sierra Leone, published a few years ago, is contained a few Ob- 
servations upon the Seasons, &c., the accuracy of which may 
be relied on. 
17. Results of a Series of Hy dr o4hermometrical Observations 
made in the Frith f Forth. — It is necessary for me to state, in 
the first place, that the observations from which these results 
were extracted, were made at the request of a friend in Leith, to 
whom I am indebted for the use of the thermometers, and also 
for much valuable information on this interesting subject. The 
observations were made with every possible care, and with as 
much regularity as my other affairs would admit of. The fol- 
lowing are the Results of my endeavours to investigate this 
branch of Natural History. 
Ist., The greatest difference in temperature between the air 
and surface-water, observed during the whole series, was 
-p8°.5 and — 9^0^'. Between the 28th of July and the 
29th of August, the mean temperature of the air and surface- 
waters was + 3°.0 and — 6°.33. The range of the thermome- 
ter in the air was observed to be, during that period, between 
62°.5 and 47° = 15°.5. The mean temperature of the surface- 
water 53.10, and that of the air 54°.95. Sc?, In the month of 
September, the mean difference of the temperatures of the air 
and surface was -{- 2°. 58, and — 3°.59. The range of the ther- 
mometer in the air during the month was between 61° and 46° 
z=: 15°, and at the surface between 56° and 51° = 5°. The 
mean temperature of the air 54°.26, and that of the surface-wa- 
ter 52°.99. 4?7i, In the month of October, the mean difference in 
the temperatures of the air and surface-water was-}- 4°and — 2°.87. 
The range of the thermometer in the air during the month was 
between 53°.0 and 39°.0 (=14°.0), and at the surface between 51° 
and 45°. The mean temperature of the air 46°.34, and that of 
the surface-water 47°.67. 5?7i, That although the temperature 
of the air has on some days varied 10°, that of the surface-water, 
on the same day, has not altered more than 1°, or 1°.5, and 
* By the sign + it must he understood that the water was warmer than the 
air, and — the contrary. 
