The following mention of an interview with Dr. Tholuck, under date May 9, 1825, is worth citing :

"Dr. Tholuck appears to be a holy man; his heart is given to God. He gave us an account of a great work of God in Berlin, Pomerania, and Weimar, which originated in the reading of Mr. Wesley's Sermons, copies of which were presented to two Prussian clergymen at our Conference in London, in 1816. These sermons have been read with avidity, and many have been brought to God in consequence. The work appears to be carried on much in the same way as among the Methodists. The Professor has a commission to procure all our standard works. I hope these will be presented to him by the Book Committee."-P. 401.

The "Wesleyan Theological Institution," for the training of young ministers, was founded in 1834. Mr. Entwisle had long made the subject of the better education of candidates for the Wesleyan ministry a subject of careful thought; and was not fully prepared, at first, to approve of the proposed Institution, thinking that some more simple and economical means of accomplishing the object might be devised. But the Committee appointed by the Conference expressed an earnest wish that he should undertake the pastoral care and superintendence of the Institution; and, after mature deliberation, he accepted the post. His appointment was universally regarded, even by the opponents of the Institution, as furnishing every guarantee that human arrangements could supply, that no loss of spiritual religion would be sustained by the candidates during their stay at the Seminary. The results of his labours there, in modifying his own views, may be seen from the following extracts, which, long as they are, will be of special interest here, where the subject of the education of the ministry is daily attracting more and more attention ::

"Having formerly entertained the opinion that the plan of placing the junior ministers in circuits under the care of experienced and judicious superintendents, competent to direct their studies and to form their ministerial character, might be preferable to that of collecting a number of young men into a collegiate institution, he was naturally led by the circumstances in which he was placed, and by the violent agitation which prevailed, to reconsider the whole subject, while the position he occupied gave him an opportunity of comparing the new plan with the old, the operation of which he had witnessed for near fifty years. A few extracts from his journal and correspondence will put the reader in possession of his views :

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January 3, 1835.-I never entered on a new year in similar circumstances: not employed in the work of a circuit, but placed in this Institution for spiritual purposes. I do most firmly believe the arrangement is providential. My soul prospers. There is much of God in our domestic worship. The family is well ordered: all is regular. The young men are evidently improving in knowledge and in piety; and I trust they will go from hence better fitted for usefulness than they would have been without such a training. I feel deeply my responsibility: much is expected: I am conscious that I am

not sufficient of myself. Yet I am not discouraged; my sufficiency is of God. He employs me, and He will help me.'

6

"In a letter to his son, written a few days after, having described his general plan of procedure, he says, Our family is a family of love: all seem to be comfortable; and our domestic worship is delightful. God is with us. Mr. Hannah's lectures, which I attend as often as I can, are most instructive and interesting: they are so, beyond anything I ever heard. They are simple and plain, yet display profound Biblical knowledge, and are attended with much Divine unction. If those who are afraid lest the institution should hurt the young men, could see and hear all that passes, they would have different

views.'

"There are some bad spirits at work. "The floods lift up their voice," but the Lord sitteth above the water-floods, and remains King forever. My mind is quite tranquil. I believe I am here by Divine appointment. I am endeavoring incessantly to do good. The young men are deeply pious and very tractable. My own soul prospers. I think I never enjoyed so much of God. I live Now. I feel dead to the world. I cease from man. I find in my God and Saviour perfect satisfaction. To Him be glory.'

"He dwelt among the students as a father among his children, cherishing the most affectionate paternal solicitude for their well-being, and receiving from them the most gratifying proof of filial confidence, respect, and love. He regularly met them in class: at first, all together; then, as their number increased, in two, and finally in three separate classes. In these weekly meetings he was close, searching, and affectionate in his inquiries and counsels: and, ever advancing before them in Christian holiness, he furnished a demonstration of its attainableness; and by an exhibition of its loveliness, supplied a powerful motive to its pursuit. And not in these meetings only,-specially instituted for purposes of Christian fellowship,-but also at all other favourable opportunities, from the fulness of his heart, he spoke to them on the subject of personal religion; at the breakfast, dinner, and tea-table,-in the garden, and by the way-side, he watched for opportunities to speak a word in season, with a view to promote among them deep experience of the things of God."-Pp. 489-495.

Mr. Entwisle held the office of Governor of the Theological Institution for four years, and then, finding repose necessary, from the weight of years and infirmities, he retired into comparative obscurity, fixing his abode in the quiet village of Tadcaster. He continued to do good in every way, as strength would allow, until 1841, when, in the seventy-fifth year of his age, he fell asleep in Jesus.

We give our cordial thanks to Mr. Entwisle, Jun., for this acceptable memoir of his venerable father, and hope that the work will find many readers on both sides of the Atlantic.

ART. X.-MECHANICS.

1. An Elementary Treatise on Mechanics, prepared for the undergraduate course in the Wesleyan University. By AUGUSTUS W. SMITH, LL. D., Professor of Mathematics and Astronomy. Harper & Brothers.

2. Elements of Natural Philosophy. By. W. H. C. BARTLETT, LL. D., Professor of Natural and Experimental Philosophy in the United States Military Academy, West Point. Lecture I.-Mechanics. New-York: Barnes & Co.

MECHANICS, the science of force and motion, has its application wherever these elements are involved in either art or nature: in the delicate machinery of the watch, and in the immense engines applied to the navigation of the ocean by steam; in the fluttering of an insect's wings, and in the mighty movements of the planetary worlds. A science which connects itself with so many objects of value and interest to mankind, is justly entitled to the high rank which it holds in public estimation, and whoever gives new developments to its principles, or better systematizes them, or simplifies their application, or renders the knowledge of them more easily accessible or more accurate, is to be regarded as a public benefactor.

The French have for years had very excellent elementary treatises on mechanics, and we have had a translation of one of them, that of Boucharlat, by Professor Courtenay, of the University of Virginia. The defect of these treatises, if so it may be called, is a want of instances of the application of the theory of the science so beautifully evolved, to the cases which actually present themselves for its application.

The works whose titles are placed at the head of this article, unite the elegant theoretic methods of the French with well-selected specimens of the practical utility of mechanics as a science; some of them handled in an original manner, and some taken from late English works. In the treatise of Professor Smith there is nothing new till we come to the chapter on "Couples," for which the author professes himself to be indebted to Poinsot. The elegance of the analytic method, aided by the calculus, begins to show itself very conspicuously, at p. 36, in the "Conditions of Equilibrium." Under the head of virtual velocities, we observe a radical difference of definition in the two treatises. What is termed the virtual velocity by Smith, is the projection of the virtual velocity according to Bartlett. At p. 60 of the former is seen the great advantage of the calculus, in determining the centre of gravity of bodies having geometric forms; and this subject is very happily managed. In the seventh chapter we have the application of the principle of virtual velocities to the mechanical powers, a beautiful and simple mode of deducing the principal theories which relate to these powers. At p. 145, the loss of living force incident to the impact of inelastic bodies is well shown, and an important practical consequence stated; namely, the inexpediency of all abrupt changes of motion in machinery. The method of determining what is termed the " modules of elasticity" in various substances, explained at p. 151, is a happy instance of the combination of experiment with mathematical for

mulæ. The chapter on the "Rotation of Rigid Bodies," at p. 190, is exceedingly well done, and presents a beautiful application of the calculus. We are particularly pleased with that part of this chapter which relates to the centre of oscillation. From p. 200 the residue of the dynamics of solids presents us with the admirable formulas of force and motion in general, and of central forces in particular, with which the readers of La Place, Pontecoulant, Poisson, &c., are familiar,-formulas which, by the aid of co-ordinate axes or lines of reference, and the considerations of the forces and movements in nature in their ultimate elements, possess a comprehensiveness that is astounding. We have never contemplated anything which caused so profound an impression of the power of the human intellect, to take in and grasp the works of the Almighty presented to its apprehension, as is to be seen in the brief analytical expressions which the calculus furnishes for the relations of all the powers of nature and their effects. The uninitiated will be incredulous when we state that the three little equations,

involve all the movements, grand and minute, in the universe.

Professor Smith, in his preface, lays "no claim to originality," but it is no small merit to have made so admirable a compilation. The work is certainly one of the best text-books on the subject extant in our language. The work of Professor Bartlett, to which in its turn we propose now to give more particular attention, has different aims, and treats the subject in a very original way; making the novel attempt to manage the most abstruse problems of mechanics without the aid of the calculus:-an attempt, the expediency or necessity of which will be questioned by some, inasmuch as the calculus is now very generally taught in our colleges, and pursued by the majority of private learners who acquire the other branches of mathematics, a knowledge of which is implied in the work before us. If it be asked how the author accomplishes the object in question, we answer that he does often in effect use the methods of the calculus or of infinitesimals, the use of which he indeed traces as he goes along. Once admitting the propriety of this grand innovation, the reader will have little other complaint to make of the work. Such clearness and brevity of statement, such skilful evasion of the dry, difficult, and tedious modes of arriving at results ordinarily thought necessary, by some ingenious short cut, through which the student clearly sees his way to the object, though he might know more about its relations if he went round about, we never recollect to have seen.

Another novelty is the starting principle of the book, which is employed all through it for the purpose of estimating and comparing results; viz., the "quantity of work." The work which "consists" in overcoming a resistance of one pound through one foot, is taken as the unit of work. This at once suggests the meaning of the term employed without further explanation, for which we must refer to p. 49 of the book. Smeaton calls it mechanical power; Carnot, moment of activity; Monge and Hachette, dynamic effect; Coulomb and Napier, quantity of action,—which is the term most commonly employed. At

p. 169 we have a most beautiful exhibition of the application of the principle of virtual velocities to machines. The mode of treating the subject of projectiles, commencing at p. 173 and again resumed at p. 220, taking into account the resistance of the air, is really quite superb. It was no more than fair, however, to expect something particularly good here in a work emanating from the Military Academy. The brevity and simplicity of this portion is not its least merit. A very elaborate chapter is that on the funicular machine, and the catenary curve. One of the very best chapters in the book is the sixteenth, on friction. This chapter contains some most valuable tables. In chapter seventeen is one of the most complete discussions of the wedge anywhere to be found, friction being taken into account, and the mode of including the effects of it in mechanical investigations most happily exemplified. Much space is given to investigation of the laws of rolling friction, in wheels, trunnions, balls, &c., with numerous tables and exemplifications. Of a similar nature, equally important and equally apt to be neglected, is the subject of stiffness of cordage, treated in the eighteenth chapter. Many pages are given on the application of all these secondary elements in calculating the action of machinery.

In the second part, which treats of the "Mechanics of Fluids," we regret to see the chapter upon the equilibruim of floating bodies so brief. Here was fine opportunity for considering some of the important problems which arise in shipbuilding, and to which we fear science, in our country at least, has not yet been sufficiently applied. Of what is given under the head of specific gravity, including the description of instruments for determining it, and tables, we must speak in high praise. Of the barometer, we have never seen a better exposition; we allude especially to the demonstrations of the rules for measuring heights with this instrument.

A book so easy to read and understand, so complete, and containing such a large amount of valuable matter, much of it not easily accessible elsewhere, cannot fail to find many students. Its "getting up" is beautiful. No pains or expense seem to have been spared. The letter-press is clear, open, and large, and the diagrams, which are exceedingly well drawn, are repeated whenever the turning over of a leaf would conceal them.

Both the above works will meet an earnest welcome in our institutions of learning.

ART. XI-SHORT REVIEWS AND NOTICES OF BOOKS.

(1.) WE welcome the appearance of "The Class-Leader's Manual, by Rev. CHARLES C. KEYS." (New-York: Lane & Scott. 18mo. pp. 223.) The class-leader is one of the most important office-bearers in our Church: the religious life of the members, as well as the financial operations of our system, depend, to a great extent, upon the leaders; who, as a body of sub-pastors, go far to make up for the inaptness of our itinerant system to regular pastoral care. Yet, important as the office is, we have not, until now, had anything