6 Mr. Harvey on the Formation 
observations ; but a farther investigation of the anomaly in question 
may lead to a satisfactory explanation of its cause. eee 
The appearance of the heavens at the time the metallic sure 
faces were placed in the meadow for observation, indicated, as be- 
fore remarked, the probability of a copious deposition of dew, 
during the night, and that a considerable quantity was deposited, 
the hoar-frost in the morning clearly proved. The temperature, 
and the hygrometric state of the air, were also, from other collate- 
ral circumstances, to be regarded as highly favourable to the for- 
mation of dew on metallic bodies; and that a breeze must have 
existed for some time during the night, sufficiently powerful, at 
least, to remove the metallic square, together with its attached 
cross, to the distance of several feet, is likewise apparent. These 
circumstances will account for the anomaly in question, * 
In the first place, dew was most probably deposited during the 
former part of the night, in a sufficiently copious degree, to cover 
the four triangles on each of the metallic surfaces. This deposition 
may be presumed to have taken place before the temperature of 
the lowest stratum of air, in contact with those surfaces, was de- 
pressed to that of the freezing point. The breeze removed the 
golden square, and left its metallic surface in contact with the short 
herbage, the temperature of which had been previously re= 
duced to 32°. This temperature necessarily caused the particles 
of dew already deposited on the triangular surfaces to crys- 
tallize ; and left the cross with its lustre undiminished. The same 
wind dissipated the moisture that had been deposited on the silver 
surface; for it has been remarked by Dr. Wells*, that ‘the dew 
which has formed upon a metal will often disappear, while other 
substances in their neighbourhood remain wet.” The breeze indeed 
may have continued the remainder of the night, and prevented any 
new formation of dew onthe silvery surface; but, at the same 
time, permitted moisture to be deposited on the non-metallic sur- 
face of the golden square ; because white paper has been placed by 
* Page Ql, Essay on Dew, hy De. Weta, second edition, 
