Some regiments adopted an entire glazed leather cap, which is assuredly much worse than the beaver, as it becomes in a short time infinitely more heated, and as soon as the soldier begins to perspire, the leather becomes moist, and attaches itself so closely to the head as to prevent all circulation of fresh air within; the confined air then, from the heat occasioned by the warm leather as well as that of the man's head, soon becomes many degrees warmer than the atmosphere.
These caps were introduced in Ceylon a short time before I left it; and I always found that the sentries and soldiers, who were for any time exposed to the sun, complained of headaches, which they attributed to the cap. I can speak from my own experience, that even at a common field-day, though in the morning, before the sun became very powerful, I was regularly attacked by a violent headache, which generally continued during the remainder of the day; though, after a much longer exposure to the sun, even during the heat of the day (when in a round hat), I felt little inconvenience.
Another disadvantage attending these caps is, that from the great trouble of cleaning them, the soldiers were in the habit, when out of sight of the officers, to take them from their heads, and carry them in a cloth, to prevent the varnish from being melted by the sun or injured by the rain; thus rather choosing to expose their bare heads to the weather than undergo the labour of repolishing them.
White, from its being the greatest non-conductor of heat, is therefore best calculated for warm climates.
The following extract from Dr. Franklin, on the subject of heat, may not perhaps prove uninteresting or useless:—
"As to the different degrees of heat imbibed from the sun's rays by cloths of different colours, since I cannot find the notes of my experiment to send you, I must give it as well as I can from memory.
"But first let me mention an experiment you may easily make yourself. Walk but a quarter of an hour in your garden when the sun shines, with a part of your dress white, and a part black; then apply your hand to them alternately, and you will find a very great difference in their warmth. The black will be quite hot to the touch, the white still cool.
"Another. Try to fire the paper with a burning glass. If it is white, you will not easily burn it, but if you bring the focus to a black spot, or upon letters, written or printed, the paper will immediately be on fire under the letters.
"Thus fullers and dyers find black cloths, of equal thickness with white ones, and hung out equally wet, dry in the sun much sooner than the white, being more readily heated by the sun's rays. It is the same before a fire; the heat of which sooner penetrates black stockings than white ones, and so is apt sooner to burn a man's shins. Also beer much sooner warms in a black mug set before the fire, than in a white one, or in a bright silver tankard.
"My experiment was this. I took a number of little square pieces of broadcloth from a tailor's pattern-card, of various colours. There were black, deep blue, lighter blue, green, purple, red, yellow, white, and other colours, or shades of colours. I laid them all out upon the snow in a bright sunshiny morning. In a few hours (I cannot now be exact as to the time) the black, being warmed most by the sun, was sunk so low as to be below the stroke of the sun's rays; the dark blue almost as low, the lighter blue not quite so much as the dark, the other colours less as they were lighter; and the quite white remained on the surface of the snow, not having entered it at all.