But the mental condition of the people had changed as greatly as the physical conditions of their environment. The immediate cause of this change was, of course, the printing press, which disseminated the thoughts of thinking men broadcast, and told of events that were occurring not only in places near, but also in places distant. This gave an enormous stimulation to the minds of the people by exciting their interest: and it also gave to their minds both "food for thought" and almost unlimited opportunity for exercise. Before this period, only a small part of the population had a wide range of knowledge, or a large number of subjects to think about. Their lives were exceedingly monotonous, and would have been exceedingly dull, had it not been for the continuous necessity of combating the inconveniences of every-day life by continual toil of one kind or another. There were very few subjects of conversation. But the printing-press told the people of other things besides the events that were taking place; it told them also of new discoveries and inventions that were being made, and of the effects they would produce. The news of a great discovery or invention must have created more excitement in 1831 when the discovery of chloroform was announced, than almost any discovery would now, because we are so accustomed to new discoveries as almost to be sated. We know what excitement the first successful railway trips created. The coming of these new discoveries and inventions gave mental exercise in four ways:--first by stimulating the imagination with a picture it had never seen before, and whose possibilities reached no one could guess how far; second by stimulating the logical powers to reason out and understand the principles underlying each discovery or invention; third by stimulating the memory to engrave upon its tablets certain new and important facts; and fourth, by stimulating the inventive faculties, to carry inventions further.