Page:Popular Science Monthly Volume 13.djvu/74

64 that the memory of children is better than the memory of adults. In truth, average children remember far less in quantity than adults, and they remember different things according to their age and taste. With children as with adults, and as with prodigies, the memory, scientifically studied, is an exact measure of mind, and in all, old and young, its limitations are so great as to impair most seriously the value of most of human testimony, even in matters of every-day life; while in all science, or the capacity of the human brain for observing systematized knowledge, for thinking and for remembering, is so limited that the world must defend, and practically, in the face of all the teachings of logicians and authorities on evidence, does defend, and rests its faith exclusively on, the testimony of experts, and in claims of new discoveries, especially against antecedent probability, on the testimony of a few only, and those of the very highest character—experts of experts—the opposing testimony of millions and millions of non-experts, though concurring and including the best and wisest of mankind, through all the ages being justly regarded as worse than worthless.



AVING thus rapidly outlined the history of the steam-engine, and of some of its most important applications, we may now take up the question—

What is the problem, stated precisely and in its most general form, that engineers have been attempting here to solve?

After stating the problem, we will examine the record with a view to determine what direction the path of improvement has taken hither-to; and, so far as we may judge the future by the past, by inference, to ascertain what appears likely to be its course in the present and in the immediate future. Still further, we will inquire what are the conditions, physical and intellectual, which best aid our progress in perfecting the steam-engine.

This important problem may be stated in its most general form thus:

To construct a machine which shall, in the most perfect manner possible, convert the kinetic energy of heat-motion, as derived from 