Page:Popular Science Monthly Volume 25.djvu/68

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60
THE POPULAR SCIENCE MONTHLY.

its preparations after washing; and grease the wheels of our carriages with another to make them run smoothly. Finally, we use the oil to burn in our reading-lamps, and light ourselves at last to bed with stearine-candles. Altogether, an amateur census of a single small English cottage results in the startling discovery that it contains twenty-seven distinct articles which owe their origin in one way or another to the cocoa-nut palm. And yet we affect, in our black ingratitude, to despise the question of the milk in the cocoa-nut.—Cornhill Magazine.


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LONGEVITY IN ASTRONOMERS.

By Dr. A. B. M. LANCASTER.

THE average length of human life in civilized countries is calculated to be about thirty-three years. This mean applies to the whole of the population of a country. But certain distinctions may be made, between different professions for example, among which considerable variations are observable. It is easy to believe that some professions would have the general effect of increasing the probable duration of life, while others would abridge it. It is generally admitted that men devoted to scientific pursuits enjoy the expectation of a considerably longer life than the average. We have been curious enough to inquire how much foundation for this opinion there is in the case of astronomers, whose observations, calculations, and studies imperiously require a quiet, sedentary, and regular life. Our investigation has been facilitated by MM. Houzeau and Lancaster's "Bibliographie Générale de l'Astronomie," in the biographical chapter of which we found all the information we needed. In this chapter are given the date of birth and death of 1,741 astronomers, of periods reaching from the most ancient times to our own days. Calculating the mean length of life of the whole 1,741, we have found it to be sixty-four years and three months. Fully to appreciate the value of this figure, we must compare it with that representing the average expectation of life at the age at which the astronomer may be supposed to have begun his career. If we fix this age at eighteen years, the person enjoys an average expectation, according to the mortality-tables, of living to sixty-one years. The astronomer, then, enjoys an advantage equivalent to an additional expectation of three years and three months. If we examine the ages to which they actually lived, we find that, out of a thousand astronomers, 596 lived to be seventy years old; 260 to between seventy and seventy-nine; 126 to between eighty and eighty-nine; 15 to between ninety and ninety-nine; and three to be over a hundred years old.

Taking a population in mass, say that of Belgium, of a thousand