104 HENRY SOTHERAN & CO., 140, STRAND, W.C, AND 37, PICCADILLY, W. 



2056 HUYGENS [Latine HXJGENITJS] (Christiaan ; f.r.s.) ffiuvRES Completes, publiees par la 

 Soci^t6 hollandaise des Sciences : Tome X : Correspondance, 1691-5 ; printed on handmade paper, 

 with numerous diagrams, thick 4to. origii.al cover, uncut, I5s (sells £1. 5* nett) La Haye, 1905 



The last volume issued, completing the author's correspondence. 



2057 -; Opera Mechanica, GeOxMetrica, Astronomica et Miscellanea, qua? coUegit, emend- 



avit, auxit atqiie illustravit etc. etc. GuiL. JAC. 's Gravesande ; with 56 folding plates, 4 vols. 

 4to. in 1, hf. cl., 16s 6d Lugd. Bat., 1751 



Containing all the author's works, except those included in the Opera Posthuma. 



2058 Opera Varia [ex recensione G. J. 's Graves andeI, with engraved portrait, and 56 plates, 



2 vols. 4to. vellum (slightly water-stained), with Prof. Williamson's auto.y \2s Qd ibidem, 1724 



2059 Another Copy, old calf (large and sound copy), los 



This is an earlier issue of the'' Opera Mechanica ', etc., with a different titlepage. 



2060 Opuscula Postuma, qu<ne continent Dioptricam, Commentarios de Vitris Figurandis, 



Dissertationem de Corona et Parheliis, Tractatum de Motu et de Vi Centrifuga, De- 

 scriptionem Automati Planetarii [ex recensione Burcheri de Volder et Bernhardi 

 FuLLENii] ; with 19 ^7ie copperplates, and numerous diagrams, 4to. contemporary Dutch calf gilt 

 (rare), 15.$ ibidem, 1703 



FiBST Edition of the author's posthumous works, afterwards republished by J. W. 's Grave.sande as Opera Reliqua, and 

 comprising Huygans's important optical works. The above works form the complete printed works of Huygens(in aLatin 

 translation), and are by no means superseded by the so-called ' Qiuvres completes ' issued by the Kon. Nederlaiidsch 

 genootschap der wetenschappen, which merely contain his correspondence. 



2061 Opera Reliqua [edente G. J. 's Gravesande] ; with bS folding copperplates, 2 vols. 4to. 



contemporary ichite parchment gilt, \1sQd Amstelodami, Vl'28 



' He constructed the pendulum-clock, following out the idea first suggested by Galileo, and developed and gave 

 precision to the lattcr's investigations upon accelerated motion under the action of gravity. By m^ans of an improved 

 telescope of his own construction, Huygens in 165.5 discovered Saturn's ring and the fourth satellite of that planet. He 

 discovered the laws of collision of elastic bodies about the same time as Wallis and Wren, and also made a material 

 improvement in the air pump. But his most important discoveries aie in the department of optics : he it was who first 

 propounded and developed what is now known as the undnlatory theory of light, and he is the discoverer of polarisation.' 



2062 De CiRCULl Magnitudine Inventa, accedunt eiusdem Problematum quorundam illus- 



triuni Constructiones ; ivith diagrams, Lugd. Bat., Joh. et Dan. Elzevier. '54: Systema 

 Saturnium, sive de Causis mirandorum SatuVni Plirenomenon, et Comite ejus Planeta Novo ; 

 ivith plate, woodcuts and diagrams, Hagw-Com., A. Vlacq, '59— in 1 vol. 4to., FINE AND large 

 copies in contemporary white vellum (RARE), £2. 2s 1654-9 



First Editions of these important works, the second containing the first account of the author's discovery of Saturn's 

 ring and his fourth satellite. It also contains at end a description of the Micrometer. 



Bound up with the above two works is ' Epistola de Mundi, quae circumferuntur, Systematis et novo alio illis certiore 

 Dialogismum paradoxum complexa : Auctore Jacobo Cocc^o' ; xvith plates, Amst., 16(50. 



2063 Exercitationes Mathematics et PniLOSOPiiiCiE ex MSS. in Bibliotheca Academia? 



Lugd. Bat. servatis edidit Petrus Joannes Uylenbroek ; with 4 folding plates, andfs., 2 vols. 

 4to. contemporary hf. calf gilt (fine copy), \2s 6o? Hagm Comit., 1833 



Containing Huygens's correspondence with Leibniz, the Marquis de I'Hospital, de Vaumesle, Fatio de Duillier, etc. etc. 



2064 HoROLOGiUM Oscillatorium, sive de Motu Pendulorum ad Horologia aptato 



Demonstrationes Geometrice, editio princeps ; with woodcuts and numerous diagrams, folio, 

 FINE tall copy in old white vellum (very rare), £3. 3* Parisiis, 1673 



'A work that ranks second only to Newton's rrincijna and con.stitutes historically a necessary introduction to it. 

 The book opens with a description of pendulum clocks, of which Huygens is the inventor. Then follows a treatment of 

 accelerated motion of bodies falling free, or sliding on inclined planes, or on given curves— culminating in the brilliant 

 discovery that the cycloii is a tautochronous curve. To the theory of curves he added the important theory of ' evolutes.' 

 ... In Huygens's assumption that the common centre of gravity of a group of bodies, oscillating about a horizontal axis, 

 rises to its original height, but no higher, is expressed for the first time one of the most beautiful principles of dynamics, 

 afterwards called the princijjle of the conservation of vis viva. The 13 theorems at the end relate to the theory of 

 centrifugal force in circular motion. This theory aided Newton in discovering the law of gravitation. '~/Vo/. Cajori. 



Added are some pp. of an old MS. bearing on the subject, and a folio leaf ' Methode aisee pour apprendre a regler et a 

 entretenir uue montre k pcndule faite par [Markham] Marwick ' [maker of 'long-case clocks ', 1720-40]. 



2065 KOSMOBEQPOS, sive de Terris Ccelestibus, earumque Ornatu, CONJECTUR.E, editio 



princeps; with 5 folding plates, sni. Ato. fine copy in old white vellum, \6s Hagcr-Com., 169S 



2066 Editio Altera ; with 5 plates, sni. 4to. old hf. vellum., lOs ib., 1699 



Published posthumously. It contains the author's views on the plurality of worlds. 



2067 [ ] Traite de la Lumiere, oii .sont expliquees les causes de ce qui luy arrive dans la 



Reflexion, et dans la Refraction, et particulierement dans I'^trange Refraction du Cristal 

 d'Islande, par C. H. D. Z., avec un Discours de la Cause de la Pesanteur ; with diagrams, er. 

 4to. newly bound in polished crimson Levant morocco gilt, cl. sides, rough g. e. {last 2 U. slightly 

 stained, otherwise a VERY TALL AND FINE COPY) ; very rare, £3 MsQd Leide, 1690 



First EoirioN of this celebrated Work, fir-st propounding his principle of 'elementary waves', enabling him to 

 explain the reflexion and refraction of light on the basis of the undulatory theory. In the ' Discours de la cause de la 

 pesanteur', which has a separate title, the author 'developed and gave precision to the investigations of Galileo upon 

 accelerated motion under the action of gravity ; and there is no doubt that to the clearness of his demonstrations his great 

 successor, Newton, in preparing liis magnificent development of the principle of accelerating force, was largely indebted.' 

 It also contains his discovery of polarisation. 



' Nach Form und Inhalt eines der ausgezeichnetsten und geistreichsten Werke der alteren Vhysik.'—Poggendorff. 



2068 HYMEKS (John, Rector of Brandesburton, F.R.S. ; founder of Hymers College, Hull) The 

 Elements of the Theory of Astronomy, 2nd Ed., revised, 4 plates, 8vo. boards, 4s 



Cambridge, 1840 



2069 Treatise on Analytical Geometry of Three Dimensions ; containing the Theory of 



Curve Surfaces, and of Curves of Double Curvature, 6 plates, 8vo. boards, 3* ib., 1830 



2070 Second Edition, altered and enlarged, 6 plates, Svo. boards, Zs Qd ib.^ 1836 



