2 Mr. Harvey on the Formation 
metallic paper, attached to frames of various forms; and by pro- 
secuting the subject under different circumstances of the atmo- 
sphere, I have met with some interesting and beautiful phenomena, 
which seem to merit a particular description. 
The metallic squares were sometimes suspended. a few inches 
above the ground, and at other times placed on surfaces of glass, 
or on the recently-mowed herbage. The particular situation of 
each will however be noticed, as the different experiments are 
described. 
In endeavouring to trace phenomena relating to the deposition 
of dew on the surfaces of polished metals, some perseverance is 
necessary ; as it is but seldom that the circumstances of tempera- 
ture and moisture are such, as to permit its ready formation. It 
would appear, that not only the depression of temperature, and the 
presence of moisture in the lowest atmospheric stratum, must be 
considerable ; but that the superficial dimensions of the metal have 
also an influence on the formation of moisture on it. ‘The dif- 
ference between glass and polished metals in this particular is sin- 
gularly remarkable. A small vitreous surface, when presented to 
a clear and tranquil sky, has its surface as readily covered with 
moisture as one of larger dimensions ; but in the case of metals of 
the same kind, of polished tin for example, a large metallic plate 
is sometimes more readily dewed than a small one ; whereas, under 
other circumstances, one of a small area is covered with a copious 
deposition of moisture, whilst a large one will preserve, during the 
whole night, a bright and unsullied surface*. I have thought it 
proper to introduce these remarks, in order to apprize the young 
inquirer of the disappointment to which he will be frequently liable, 
when prosecuting this interesting subject with relation to polished 
metals. 
Whenever the squares of silver paper were exposed for the pur= 
* ‘A large metallic plate, lying on grass, resists the formation of dew more 
powerfully than a very small one similarly situated. If a large and a very 
small plate be suspended horizontally, at the same height in the air, the small 
plate will resist the formation of dew more powerfully than the large.”’— 
Wexts on Dew, page 22; second edition. 
