136 
Proceedmgs of the, Royal Society 
The picture is that of a sloop floating on a calm sea with its 
shadow in the water ; the sharpness of the image is considerably 
overdone, very few, persons have seen it so sharp. But the charac- 
teristic feature is there ; the image and the ship are united at the 
water-line it is a well known and understood appearance. 
Oh ! but Vince saw it up in the air ! 
When the sea is smooth, the reflection of the sky from the water 
and the light of the sky itself are so nearly balanced as to be 
undistinguished, hence the difficulty (sometimes amounting to im- 
possibility) which the seaman has in bringing down the sun to the 
water-edge. He is unable to tell where the sea ends or the sky 
begins. 
When the breath of a zephyr touches such a sea, it causes a dark 
space which is foreshortened into a narrow streak. Such streaks 
are apt to be mistaken for the true horizon, and the sailor-appren- 
tice may find himself wrong in his latitude ; but the mate or the 
captain has been on his guard. 
Here, then, is the whole diagnosis of Vince’s drawing:' — He 
had seen a sloop floating on a very calm sea, the captain had taken 
the opportunity to air his canvas, some stray spars or some sea- 
weed had been on the edge of a ripple in-shore, and the Pro- 
fessor’s powerful imagination had manufactured wonders out of the 
vision. 
2. On the Thermo-electric Positions of pure Ehodium and 
Iridium. By Professor Tait. 
3. Observations on the Growth of Wood in Deciduous and 
Evergreen Trees. By the late Sir K. Christison, Bart., 
and Dr Christison. 
4. The Variation of Temperature, with Sun-Spots. By Mr A. 
Buchan. 
