In various manufactures, such as ore smelting, and in the manufacture of glass, china and pottery, in enamelling and in certain engineering shops, where it is necessary to examine material at a high temperature, the micro-telescope is a great boon, and, at least, is the means of avoiding considerable physical discomfort. It is used also by architects and surveyors for examining the condition of the factory chimneys, bridges, derricks and the like. To the engineer the instrument is invaluable; we have explained elsewhere how necessary it is that various metals and mixtures of metals should be examined for fractures. Under the high magnification with the ordinary microscope, even with an instrument specially designed for the work, only a very small area can be studied at once. With the micro-telescope a relatively large area may be examined under a high magnifying power. There are three features of this ingenious apparatus which cannot fail to commend themselves equally to the casual worker and the serious microscopist. All objects are seen erect, just as the eye sees them. This is brought about because, as in the case of the super-microscope, we really observe a magnified, inverted image of our object, formed at the spot where the object would be placed were we using an ordinary microscope. This image is inverted once more in the microscope and so it appears to us erect. All objects appear in relief and in their proper planes; this is seen in a striking manner by viewing an ordinary photograph through the apparatus, when the various parts stand out as in nature. There is also enormous depth of focus. With the attachment for viewing objects at a short distance, the whole of a tubular shaped flower such as a daffodil may be in focus at once, from the tip of the petals to the bottom of the tube. With the attachment designed for long distance work, objects from twenty yards to sixty miles may be clearly viewed at one and the same time. A few of the unsolved problems confronting the microscopist are reviewed in our concluding chapter. Whether they will ever be solved we dare not venture to say; but, if they are to be, surely to this latest arrival in the microscopic world and to its companion, the super-microscope, the honours will go. CHAPTER XVIII CHEMISTRY AND THE MICROSCOPE To thoroughly comprehend the various uses to which the chemist may put his microscope, it is necessary to have a knowledge of chemistry. The science is so wide in its scope that no single chapter could do justice to it. There are analytical chemists, scientists whose aim is to find out the composition of various substances; biological chemists who deal with the many problems of life in which chemistry plays a part, but we need not attempt to detail all the branches of this highly specialised science.