any participant in the excellent work of that organization, he can not, in good English, be less than an assistant, and yet only officers of the highest attainable grade are entitled to the latter distinction. Still below the assistants and sub-assistants come the aids, young officers whose inferiority of position is mollified by the possession of a title synonymous in meaning with that of their superiors, and therefore equally respectable in the popular comprehension. Such is the poverty of this nomenclature that it carries with it only the general idea of subordination. Surely it would not be impossible to devise some system of titles which would at the same time convey some hint of the duties and the relative rank of the scientists of that body.
SCIENTIFIC discoveries are not distributed uniformly in time. They appear rather in periodic groups. Thus, in the first two years of this century, among other gifts presented by men of science to the world, we have the voltaic pile; the principle of Interference, which is the basis of the undulatory theory of light; and the discovery by William Herschel of the dark rays of the sun.
Directly or indirectly, this latter discovery heralded a period of active research on the subject of radiation. Leslie's celebrated work, "On the Nature of Heat," was published in 1804, but he informs us, in the preface, that the leading facts which gave rise to the publication presented themselves in the spring of 1801. An interesting but not uncommon psychological experience is glanced at in this preface. The inconvenience of what we call ecstasy, or exaltation, is that it is usually attended by undesirable compensations. Its action resembles that of a tidal river, sometimes advancing and filling the shores of life, but afterward retreating and leaving unlovely banks behind. Leslie, when he began his work, describes himself as "transported at the prospect of a new world emerging to view." But further on the note changes, and before the preface ends he warns the reader that he may expect variety of tone, and perhaps defect of unity, in his disquisition. The execution of the work, he says, proceeded with extreme tardiness; and, as the charm of novelty w r ore off, he began to look upon his production with a coolness not usual in authors.
The ebb of the tide, however, was but transient; and to Leslie's ardor, industry, and experimental skill, we are indebted for a large body of knowledge in regard to the phenomena of radiation. In the prosecution of his researches he had to rely upon himself. He devised
- A "Friday Evening Discourse," recently delivered in the Royal Institution.