Dec. 29, 1887] 



NA TURE 



195 



I consider that no definite conclusion can be arrived at." 

 He further dechires that the esoteric form of the Society's 

 symbol was a rose in the centre of which is figured a 

 Latin cross : he calls attention to the seal of Luther, on 

 which a heart, surmounted by a cross, is inclosed by the 

 outline of a rose, and hence gathers that the unknown 

 founders of the Society chose this emblem, not from any 

 recondite associations, but simply because the reforming 

 monk was their idol. 



With the case of Johann Valentin Andreas the interest 

 of the work culminates. When we have learnt that nothing 

 can be determined, and that there is every reason to 

 believe that could we probe the heart of the mystery we 

 should find little to reward our search, we care little for a 

 record of the progress of Rosicrucianism in France and 

 Germany, or for the writings and biographies of Rosicrucian 

 apologists such as Michael Maier, Robert Fludd, Thomas 

 Vaughan, and John Heydon. Artistically, this continuation 

 is an anti-climax, and the chapters which compose it might 

 have been fittingly relegated to the appendix, together with 

 those remaining sections which are devoted to a refutation 

 of the claims of the Freemasons and of modern Rosicrucian 

 Societies to connection with the original fraternity of the 

 Rosy Cross. 



The claim which Mr. Waite puts forward to be considered 

 an impartial historian we readily admit, for we have rarely 

 seen a work of this description that was so free from all 

 attempts at the distortion of facts to dovetail with a pre- 

 conceived theory. His style is perspicuous, and contrasts 

 most favourably with that of his Rosicrucian rival, Mr 

 Hargrave Jennings, against whom he tilts with much 

 vigour throughout his pages. 



The most interesting portions of the book are those 

 where the author is willing to speak himself; for the 

 lucubrations of the illummati, which fill some 250 out of 

 the 446 pages composing the work, are for the most part 

 msipid and fatuous to the lay mind. It was doubtless 

 necessary to include transcripts of the "Fama" and the 

 " Confessio," these being the authoritative expositions of 

 the Society's views, but we could have spared much of 

 the "Chymical Marriage," and all of the "Universal 

 Reformation of the Whole World by order of god Apollo " 

 which Mr. Waite describes as a fairly literal translation 

 of advertisement 77 of Boccalini's " Ragguagli di Par 

 nasso,-Centuria Prima," and which, he adds, " throws no 

 light upon the history or claims of the Rosicrucians " 

 Neither is much learnt from the speculations of the apolo 

 gists whose philosophy, although mysterious, is not to be 

 readily Identified with that of the fraternity as officials 

 set forth In wading through such documents, one is 

 reminded of Mr. Shandy's exclamation when Rubenius 

 has furnished him with information on every conceivable 

 point except upon the one on which he sought for it The 

 work on the whole is well done and satisfactorily produced 

 but It lacks an index. Had the author furnished as good 

 an index to his volume as the enterprising publisher, Mr. 

 Redway has added to his advertisements, he would have 

 enhanced its value as a book of reference. To those 

 students of occultism whose palates, undebauched by the 

 intellectual hasMsh of the rhapsodies of mysticism and 

 the jargon of the Kabala, can still appreciate a plain 

 historical statement of facts we gladly commend the 



THE MECHANICS OF MACHINERY. 

 The Mechanics of Machinery. By Alex. B. W. Kennedy, 

 Professor of Engineering and Mechanical Technology 

 in University College, London. (London : Macmillan 

 and Co, 1886.) 



A LTHOUGH the author explains in his preface that 

 ^»- this work is destined to meet the requirements of 

 young students of engineering, still the mathematical 

 student of mechanics would reap immense benefit from 

 a careful study of the novel treatment presented here, 

 and would recognize the shortcomings and unsatisfactori- 

 ness of the treatises usually put into his hands. 



Here we have a treatise on real mechanics, with dia- 

 grams, drawn accurately to scale, of real machines, and 

 illustrative examples drawn from real life, while the 

 ordinary mathematical treatise put into the student's 

 hands is generally a great contrast, by reason of its 

 abstract method of treatment, the unpractical nature of 

 the problems discussed, and its diagrams resembling 

 nothing that ever existed, purposely drawn badly, for 

 the reason, it is urged, that a bad draughtsman can copy 

 them more easily. 



Prof. Kennedy, in his preface, explains how he has 

 been driven to the vernacular use of the word " pound " 

 as a name for a unit both of weight and of force, as " the 

 adoption of any other plan would have made the book 

 practically useless to almost all engineers so long as the 

 thousand-and-one problems of their every-day work come 

 to them in their present form." This plan is so perfectly 

 clear and intelligible to ordinary practical men to whom 

 dynamical problems on a large scale are a reality and 

 not a mere theoretical abstraction that it is a pity that 

 Prof. Kennedy has gone back on his principles in insert- 

 ing in § 30, on force, mass, and weight, an attempt at 

 explanation of the confusion of ideas in books on mech- 

 anics written by mathematicians, due to the introduc- 

 tion of the word "mass," a word which the engineer 

 never requires. 



The explanation of the relation between force, weight, 

 and acceleration is so simple that it may very well be given 

 here. Taking the gravitation unit of force, universally 

 employed by our engineers, as the attraction of the earth 

 on a weight of one pound, and calling this \ht force of one 

 pound, then a force of /pounds acting on a weight of w 



pounds will produce acceleration a, such that -^ =- hv 



w ^ ' -^ 



Newton's Second Law of Motion ; or. /= ^^. 



S 

 But, if V is the velocity acquired in feet per second, 

 and s the number of feet described in t seconds from rest, 

 then it is shown in Chap. VII. of the present treatise 



that V = at, \v^ = as ■ so that // = — ^ , and fs = ^^^ • 

 Here fs represents the work done on the body in foot- 

 pounds of work, and the dynamical equivalent is ^^^ 

 foot-pounds of kinetic energy. 



So also the product // is called the impulse, in second- 

 Pounds, of the force / acting for the time /, and its 



dynamical equivalent is ~- units of momentum, the 



momentum of w pounds moving with velocity v being 

 defined by the product nnj. 



