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Abstract

DR. WATTS is to be congratulated upon the completion of his great undertaking—namely, to collect all the existing measurements of laboratory spectra, and arrange them in a manner convenient for reference. Since the last edition of the book was published, seventeen years ago, spectroscopic research has made enormous progress, as a comparison with the new edition will show. This is no doubt partly due to the increased number of workers, and instrumental advances, and to a large extent to the extension of the spectroscopic field into the ultra-violet and infra-red. In the old tables the limits of the spectra were practically 394 and 670, whereas in the new ones the lines range from 204 to 770. Spectroscopy has also advanced in another direction. It was formerly believed that each substance had its own characteristic spectrum, from which there was no departure; but subsequent researches have shown that the spectrum does not entirely depend upon the substance under examination, but also upon the conditions of temperature and pressure. In the old tables, for example, only one spectrum of oxygen was recorded, but now no less than three are given. Hydrogen, again, has now two spectra recorded, and nitrogen three, including Hasselberg's important observations.

Index of Spectra.

By (W. Marshall Watts, ©. Revised Edition. Manchester: Abel Heywood and Son, 1889.)