162 Proceedings of Royal Society of Edinburgh. [sess. 
particles doing all the radiation, and the upper layers protecting 
the lower ones. The temperature on the grass was warmer than at 
4 feet up. 
On the 5th of January observations were made on the number of 
dust particles in the air at Ballantrae, a small village on the coast 
of Ayrshire. This place w T as selected with a view of testing the 
condition of the air resting on the sea. Though the day was one 
in every way suited to the purpose, the results are of little value. 
The wind was very slight, moving with but a gentle motion from 
the south-west — that is, towards shore — so that the air that had 
been resting on the sea was brought direct to the apparatus ; yet 
the number counted was as high as 5000 per c.c., though the air 
that day was clear and bright. This large number was not caused by 
any artificial impurities, as the place of observation was close to the 
shore and within 50 yards of the water. The great number counted 
was evidently in part due to the action of the small waves breaking 
on the shore. Though very small, little more than a ripple, yet 
these waves manufactured a vast quantity of water particles, which, 
though they might dry, would yet leave a salt particle as residue. 
One would scarcely have expected this result from such small 
waves, and we might have felt inclined to accept the number as 
correct for sea air. Owing, however, to the atmospheric conditions, 
I was able to observe that the very small waves were manufacturing 
vast numbers of particles. The day was very clear, with bright 
sunshine ; and on looking along the shore-line close to the sea, the 
bright sunshine disclosed the existence of a perfectly distinct mist 
all along the shore, where the little waves were breaking. With a 
stronger wind, or a more rapid evaporation, these manufactured 
particles might not have been visible. For observations on sea air 
it will be necessary to select calm weather, and make the tests in 
a boat at some distance from shore. The numbers obtained at 
Ballantrae are therefore far too high for sea air at the time and 
place, and the impurity in the air tested there was probably salt 
particles. At sea, if there is as much wind as will break the sur- 
face, there will be manufactured vast quantities of salt dust, and 
the number of these particles will probably vary with the force of 
the wind. 
During the past year a great number of tests have been made of 
