This remarkable force of the sun’s rays is accompanied with a corresponding intensity of light. A person placed in the centre of a field or other compact body of ice, under a cloudless atmosphere and elevated sun, experiences such an extraordinary intensity of light, that if it be encountered for any length of time, is not only productive of a most painful sensation in the eyes, but sometimes of temporary, or even, as I have heard, of permanent blindness. Under such circumstances, the use of green glasses affords a most agreeable relief. Some of the Indians of North America defend their eyes by the use of a kind of wooden spectacles, having, instead of glasses, a narrow perpendicular slit opposite to each eye. This simple contrivance, which intercepts, perhaps, nine-tenths of the light that would reach a naked eye, prevents any painful consequences in the most intense reflection of light that ever occurs. The constant light of the sun during the summer prevents the stars from being seen; and this, together with the frequency of cloudy or foggy weather, rarely admits a sight of the moon. Hence, the longitude, which is of such essential importance in navigation, can seldom be determined by lunar observations. Chronometers, therefore, though but little used by the whale-fishers, become of enhanced value; and even a good watch, well regulated, will, where the degrees of longitude are so very contracted, point out the meridianal situation of the ship for short intervals, with a very tolerable degree of accuracy. Though the air in the arctic seas is generally in a state of dampness, approaching to complete saturation, yet the absolute quantity of moisture cannot, when the cold is very excessive, be considerable. It is remarked, that vessels are less apt to rust here than in any other climate; and this observation, if we consider the relative humidity of the atmosphere as indicated by the hygrometer, is certainly correct; but though the air in the Polar regions is generally damp, yet it is probable there is no habitable situation in the known world in which such a degree of actual dryness prevails, as in a house or in the cabin of a ship, well heated, when the external air is intensely cold. The wainscoting of the cabin of a ship in cold weather sometimes shrinks, in consequence of the uncommon dryness, as much as half an inch in a panel of about fifteen inches broad, being equal to one-thirtieth of the breadth; but, on returning to Britain, the same panel expands again to almost its original dimensions.