[14] _The Half Century; or a History of changes that have taken place, and events that have transpired, chiefly in the United States, between 1800 and 1850_; with an introduction by Mark Hopkins, D.D. By Emerson Davis. D.D. Boston: Tappan & Whittenmore. POPULAR LECTURES. Thus far this season, there has been even more than the usual amount of lecturing in our principal cities. The mania lasts longer than was thought possible. The "phenomenon" has really become a feature of the times. It absorbs a great share of the current literary enthusiasm--much of which it has created, and will, it is to be feared, entirely satisfy. Professor Pease, of the University of Vermont, in an essay upon the subject, seeks to determine its import and value; to trace the feeling which gives it birth to its source, and to determine as accurately as possible the grounds of promise or of fear which it affords. "These interpretations," he says, "vary between the widest extremes. On the one side is heard the exulting shout of those who whirl unresistingly in the vortex--'Does not wisdom cry and understanding put forth her voice?' behold the 'progress of the species' and the 'march of mind!' And, on the other side, the contemptuous murmur of those who will be overwhelmed rather than gyrate against their will, they know not whither--'What meaneth this bleating of the sheep in mine ears?'" This mania for lectures, taken in connection with the prevailing literary taste (of which it is in some sort an index), is regarded as pointing, more or less directly, to a want of the human spirit--to its cry--strong and importunate, though often stifled and but dimly felt, for light--the light of science and of truth. Many feel this want only as a _traditional_ need--one which their fathers before them have felt and have taught them to feel--and _they_ are apt to be satisfied with a traditional supply. Others ask for science because it will help them make, or work, and perchance _become_ machines, whereby they may earn bread: and oftentimes, says the writer, "does this mere irritability of the coating of the stomach pass itself off as the waking up the life of the soul, and the sublime and pure aspirations of the spirit, for high and ultimate truths, pure as itself." Then, it is the fashion to be learned, and the fops of literature, who must "follow the fashion," of course, get wisdom as quickly and easily as possible. These are the main features of that demand for science, which is now so clamorous. Mr. Pease divides the lectures of the day into three classes; first those of which the object is instruction, then those designed to amuse, and last, those which profess to serve both these purposes; and he thinks it may be said of all, that they have no _vital, form-giving, organific principle_, running through them, developing properly each separate part, and uniting them all by its own power.