A small instrument, used in the infrequent intervals which may be all that can be snatched from the claims of other work, will give the user a far more intelligent interest in the sun, and a far better appreciation of its features, than can be gained by the most careful study of books. In this, and in all other departments of astronomy, there is nothing like a little practical work to give life to the subject. In the conduct of observation, however, regard must be paid to the caution given at the beginning of this chapter. Various methods have been adopted for minimizing the intense glare and heat. For small telescopes--up to 2-1/2 inches or so--the common device of the interposition of a coloured glass between the eye-piece and the eye will generally be found sufficient on the score of safety, though other arrangements may be found preferable. Such glasses are usually supplied with small instruments, mounted in brass caps which screw or slide on to the ends of the various eye-pieces. Neutral tint is the best, though a combination of green and red also does well. Red transmits too much heat for comfort. Should dark glasses not be supplied, it is easy to make them by smoking a piece of glass to the required depth, protecting it from rubbing by fastening over it a covering glass which rests at each end on a narrow strip of cardboard. With anything larger than 2-1/2 inches, dark glass is never quite safe. A 3-inch refractor will be found quite capable of cracking and destroying even a fairly thick glass if observation be long continued. The contrivance known as a polarizing eye-piece was formerly pretty much beyond the reach of the average amateur by reason of its costliness. Such eye-pieces are now becoming much cheaper, and certainly afford a most safe and pleasant way of viewing the sun. They are so arranged that the amount of light and heat transmitted can be reduced at will, so as to render the use of a dark glass unnecessary, thus enabling the observer to see all details in their natural colouring. The ordinary solar diagonal, in which the bulk of the rays is rejected, leaving only a small portion to reach the eye, is cheaper and satisfactory, though a light screen-glass is still required with it. But unquestionably the best general method of observing, and also the least costly, is that of projecting the sun's image through the telescope upon a prepared white surface, which may be of paper, or anything else that may be found suitable.