As to the practical efficacy of this preventive, the experience of France, where it is universally practised, might suffice in proof. We know, at this moment, several married persons who have told us, that, after having had as many children as they thought prudent, _they had for years employed it with perfect success_. For the satisfaction of our readers, we will select some instances. A few weeks since, a respectable and very intelligent father of a family, about thirty-five years of age, who resides west of the mountains, called at our office. Conversation turned on the present subject, and we expressed to him our conviction that this preventive was effectual. He told us he could speak from personal experience. He had married young, and soon had three children. These he could support in comfort, without running into debt or difficulty; but, the price of produce sinking in his neighborhood, there did not appear a fair prospect of supporting a large family. In consequence, he and his wife determined to limit their offspring to three. They have accordingly used it for seven or eight years; have had no more children; and have been rewarded for their prudence by finding their situation and prospects improving every year. The next communication from which we shall copy is from a young man of excellent character, living in a neighboring state, and now one of the conductors of a popular periodical. After suggesting to us the propriety of re-publishing some English works now out of print, he proceeds as follows: “Had I not been addressing you upon another subject, I should not have ventured to obtrude on you my small need of approbation; but I cannot let slip this opportunity of endeavoring to express how much I feel indebted to you for its publication. “To know how I am so indebted, it is necessary you should also know something of my situation in life; and when it is described, it is perhaps a description of the situation of two-thirds of the journeymen mechanics of this country. “I have been married nearly three years, and am the father of two children. Having nothing to depend upon but my own industry, you will readily acknowledge that I had reason to look forward with at least some degree of disquietude to the prospect of an increasing family and reduced wages: apparently the inevitable lot of the generality of working men. “I had apparently nothing left but to let matters take their own course, when your valuable work made its appearance. “I read it; and a new scene of existence seemed to open before me. I found myself, in this all-important matter, a free agent, and, in a degree, the arbiter of my own destiny. I could have said to you as Selim said to Hassan,—‘ ‘Thou’st hew’d a mountain’s weight from off my heart.’