microscopes were a rarity in America. In the year 1840, when the United States Exploring Expedition to the South Seas, under Commander Wilkes, was fitting out, it was thought necessary to have a microscope. The various makers of scientific and philosophic instruments were applied to, but none of them could furnish the expedition with the thing desired. In this dilemma a private individual was appealed to, and an instrument thus finally obtained, in the shape of an inferior French microscope. How, then, did the present flourishing state of affairs come about? Simply by the genius of a self-taught man. He was a backwoodsman, and had pored over an old cyclopædia, and turned the optical knowledge contained therein, as far as in him lay, to sound practical account. At the age of twelve years he made his first lens. One day he happened to be shown a microscope constructed by Chevalier, of Paris, and the thought struck him that he would try to make a similar instrument. He succeeded, and his glasses were able to resolve a test which similar objectives of the first English opticians had hitherto failed to define. His name was Charles Spencer. And now his pupil Tolles, and Wales, a pupil of Smith and Beck, with Gronow, Zentmayer, and others, form a galaxy of American mathematical instrument talent that appears from recent accounts to be holding its own against the whole of the world. Is there not here a ground for the hope I expressed a little while ago? Surely after this example of Spencer, the young backwoodsman, many here present may live to see the day when a finished microscope shall be presented to their delighted gaze by the hands of an Australian townsman, at least, if not by an Australian bushman."
The Improvement of Human Life.—An extremely valuable paper by Dr. Edward Jarvis, on "Political Economy of Health," published in the Fifth Annual Report of the Massachusetts Board of Health, groups together very strikingly the vital statistics of various countries, to show the effect of the advance of civilization in protracting the term of human life. By better adaptation of means, circumstances, and habits, says Dr. Jarvis, man's life has been expanded, his strength increased, and his days on earth prolonged. By the improvements in agriculture and in vegetable and animal life, he has obtained better and more constant food, and is therefore better nourished. By the improvements in the arts he is better clothed and housed, better protected from the elements. The progress of civilization is best manifested in the progress of vitality. There is less sickness, and that which visits humanity is less destructive than in former ages.
In ancient Rome, in the period 200 to 500 years after the Christian era, the average duration of life in the most favored class was 30 years. In the present century the average longevity of persons of the same class is 50 years. In the sixteenth century the average longevity in Geneva was 21.21 years; between 1814 and 1833 it was 40.68, and as large a proportion now live to 70 as lived to 43 three hundred years ago. In 1693 the British Government borrowed money by selling annuities on lives from infancy upward, on the basis of the average longevity. The treasury received the price and paid the annuities regularly as long as the annuitants lived. The contract was mutually satisfactory and profitable. Ninety-seven years later Mr. Pitt issued another tontine or scale of annuities, on the basis of the same expectation of life as in the previous century. These latter annuitants, however, lived so much longer than their predecessors, that it proved to be a very costly loan for the Government. It was found that while 10,000 of each sex in the first tontine died under the age of 28, only 5,772 males, and 6,416 females in the second tontine died at the same age one hundred years later. The average life of the annuitants of 1693 was 26.5 years, while those of 1790 lived 33 years and 9 months after they were 30 years old.
From these facts, says Dr. Jarvis, it is plain that life, in many forms and manifestations, and probably in all, can be expanded in vigor, intensity, and duration, under favorable influences. For this purpose it is only necessary that the circumstances amid which, and the conditions in which, any form of life is placed, should be brought into harmony with the law appointed for its being. By this means the intelligent world
