A HISTORY OF THE THERMOMETER.
Dr. H. Carrington Bolton is one of the few Americans acquainted with the history of science, and his little volume on the evolution of the thermometer (The Chemical Publishing Company) represents a type of publication too rare in this country. The scientific information is correct throughout and is based on first hand knowledge, while at the same time the contents are sufficiently interesting to be read by any one. It is probably not generally known that the thermometer was invented by Galileo. When we remember that we owe to this one man not only the foundations of physical science, but also in large measure the pendulum, the compass, the telescope and the microscope, it may lead to a certain amount of modesty in our appreciation of modern inventions. Galileo, probably in 1595, invented the open air thermoscope; he determined the relative temperature at different places and at different seasons of the year and made experiments on freezing mixtures. In 1611 Sanctorius applied Galileo's instrument to the diagnosis of fevers. Ferdinand II. of Tuscany, to whom we owe the famous 'Accademia del Cimento,' first sealed the glass, making the instrument independent of atmospheric pressure. Many improvements were gradually made especially in the endeavor to find fixed points on a definite scale, the freezing point of water being first used by Robert Hooke in 1664. Of the three thermometers still in use, Fahrenheit's thermometer was invented in 1709, Réaumur's instrument in 1730 and the scale of Celsius in 1742. None of these thermometers, however, are now used in the form in which they were originally devised, and Dr. Bolton calls attention to the somewhat curious fact that the instrument constructed by the German, Fahrenheit, is used almost exclusively by English speaking peoples; that invented by the Frenchman, Reaumur, is used chiefly in the north of Europe, while that of the Swede, Celsius, is used in the French speaking countries. Dr. Bolton does not attempt to compare the usefulness of the three scales. The centigrade scale is, of course, the most logical, but, as sometimes happens in this world, it is not quite certain that it is the most convenient. When the scale of temperature between freezing and boiling water is divided into one hundred parts, the degrees seem to be somewhat too large for use in daily life, whereas if it were divided into one thousand parts they would be obviously too small. It is possible, however, that this is Anglo-Saxon prejudice, and that the centigrade degree measures temperature with sufficient accuracy for ordinary purposes, while its decimal subdivision must certainly be used hereafter for scientific work. Dr. Bolton's book is so small that it seems a pity that he did not add a chapter on the exact thermometric methods of the nineteenth century.
Professor E. B. Titchener, of Cornell University, has given us our first adequate laboratory manual of experimental psychology and has thus marked an epoch in the development of a science. Experiment in psychology, like much else, goes back to Aristotle, and has never since been entirely lacking. The great philosophers—Descartes, Hobbs, Kant and the rest—advanced