158 



scmJsrcE. 



LVoL. IX., No. 211 



generally found in French grammars, I have treated, 

 in eacli of those exercises, one special subject. 



I have made a synoptic table of thirteen lines, by 

 which all verbs, regular or irregular, are conjugated, 

 thus saving the student the monotony and annoyance 

 of studj'ing the verbs from memory by a new com- 

 bination and arrangement. The student is thereby 

 saved loss of time in writing endless conjugations of 

 verbs. 



To make attractive and instructive a study which 

 is too often wearisome and sterile, I have given, in 

 the third volume of my series, a vocabulary, divided 

 into chapters, each containing an interesting outline 

 of stories bearing on a special subject, and compris- 

 ing a list of the most useful and important words of 

 the language in daily iise. Thus a natural chain of 

 ideas is formed, easily remembered, and which can 

 be made the subject of a conversation a^id composi- 

 tion, the student gaining in this way a thorough 

 knowledge of the practical framework of the lan- 

 guage. As soon as the student knows a few words 

 of the vocabulary, these outlines are made the sub- 

 jects of conversations between teacher and pupils, 

 and, later on, between the piipils themselves. They 

 are also employed in the form of narratives, by join- 

 ing them together ; and, by degrees, they are en- 

 larged upon more and more. The fourth volume of 

 my series, ' The modern French method,' comprises 

 a series of words, idioms, and proverbs, forming 

 skeleton narratives of travel, incident, and scenes, — 

 romantic, dramatic, and comic, — all fitted to elevate 

 the mind and inspire noble thoughts : there are 

 also sketches in geography, biography, and history 

 to be used in conversation and composition. By the 

 study of this work, the learner acquires the frame- 

 work, words, and idioms for literary style ; and as 

 every word, idiom, and proverb is properly located, 

 the student will comprehend all their bearings by 

 the context, and will know how to use them in their 

 full meaning. A vast number of idiomatic questions 

 are put upon the above-mentioned outline, and the 

 answers are furnished by the student from the skele- 

 ton, or framework, upon which he enlarges at will. In 

 order that the learner should acquire self-reliance, and 

 be able to express himself freely on literary subjects, 

 and should get an elegant style of his own, he sets 

 down in narrative form each lesson previously 

 treated conversationally, by which means he can 

 give free play to his imaginative faculties. 



The iDupil, being constantly imbued with French 

 ideas, and accustomed to look at things from a French 

 point of view, adapts himself to them, and neces- 

 sarily expands his mental vision : and as a great 

 number of the subjects he treats of arouse his moral 

 sensibility, and are fitted to excite in his heart tender 

 compassion, brotherly love, devotion to his fellows, 

 and self-denial, his moral capacities must be, as a 

 matter of course, enlarged. This method is easy 

 and simple, interesting, natural, and practical ; and 

 it relieves the student from much irksome and monot- 

 onous labor. It trains the ear to the apprehension 

 of the spoken language, and, by a systematic train- 

 ing of the vocal organs, gives to the speaker a 

 faultless Parisian pronunciation. The pupil is 

 presented with a vocabulary so constructed that all 

 the words, idioms, and proverbs form an intelligible 

 outline of scenes and sketches, which the mind grasps 

 and retains, while bringing out fully their individ- 

 ual and conventional meanings. The pictures are 

 made so vivid and obvious, and the words are so 



suggestive, that the memory is greatly assisted, and 

 the aquirement of a stock of words becomes a mere 

 pastime. These words are fixed in the mind of the 

 student by frequent and pleasant repetition, and thus 

 memory is cultivated without straining ; while, by 

 means of idiomatic questions, educing appropriate an- 

 swers, the learner is made acquainted with the peculiar 

 genius of the French language. No English is either 

 written or uttered during the course. The pujDil finds 

 in the book ample English explanations, and is never 

 left in the dark ; yet by degrees he becomes accus- 

 tomed to think in French. 



Joseph D. Gaillakd. 

 New York, Feto. 11. 



Inertia-force. 



In Science of Feb. 11 Professor MacGregor has 

 very courteously criticised my use of the idea which 

 I have sought to express by the term ' inertia- 

 force ' in a pamphlet recently published. Professor 

 MacGregor misunderstands me, however — or I mis- 

 understand him. He quotes from my pamphlet the 

 following passage : '' If one of the opposing applied 

 forces is greater than the other, the greater will pre- 

 vail, and a change of motion will occur, occasioning 

 an inertia-force, which will vjovk. with the smaller 

 applied force against the greater," and then says, 

 " The inertia-force, therefore, is supposed to act on 

 the body by which it is exerted." 



I am at a loss to understand how Professor Mac- 

 Gregor makes this inference from the passage he 

 quotes. I meant that the inertia-force works (' acts ' 

 would be a better word) with the smaller applied 

 force against the agent which exerts the greater 

 force. Take this example : a train is being started 

 by a locomotive. The forces applied to the train are 

 the pull of the locomotive, and the smaller, opposing, 

 force of friction. The pull of the locomotive pre- 

 vails, but in prevailing it must deal not only with the 

 resistance due to friction, but with the reaction 

 (which also I call resistance) due to the inertia of the 

 train. The friction resistance would be nearly the 

 same whether the accelei'ation of the train were 

 great or small ; but the resistance due to inertia, the 

 inertia-resistance , or inertia- force, would be always 

 proportional to the acceleration. 



The term ' centrifugal force,' although I do not 

 like it, does not excite in me the horror which Pro- 

 fessor MacGregor evidently thinks it should occa- 

 sion. I certainly should not say that a ball swinging 

 in a circle at the end of a string connecting it with 

 the centre of the circle is acted on by 'a force di- 

 rected from the centre,' but I certainly should say 

 that the ball acts upon the string with ' a force 

 directed from the centre,' — a proposition which 

 seems to me so plainly true thab I think all difference 

 of opinion as to its truth must arise from different 

 interpretations of the word ' force ' 



I suspect that Professor MacGregor and I do in- 

 terpret that word somewhat differently. The fol- 

 lowing quotation from Maxwell's ' Matter and mo- 

 tion,' p. 78, seems to me to express my view with 

 sufficient accuracy : — 



"As soon as we have formed for ourselves the 

 idea of a stress, such as the tension of a rope or the 

 pressure between two bodies, and have recognized 

 its double aspect as it affects the two portions of 

 matter between which it acts, the third law of mo- 

 tion is seen to be equivalent to the statement that all 

 force is of the nature of stress, that stress exists 



