362 



NATURE 



[August i8, i. 



out altering the figure. His defence of Newton's con- 

 struction against the objections of Cassegrain is reprinted 

 in this volume from the Journal des Savants. With 

 Newton himself Huygens does not seem to have been in 

 direct communication, but through Oldenburg the 

 doubts of the Dutch philosopher as to the actual number 

 of colours in the sun-spectrum were brought to the 

 knowledge of Newton, who replied to them in two 

 papers printed in the Philosophical Transactions and 

 reprinted in the present volume. The first and last 

 pages of one of the papers, which was written in the 

 form of a letter to Oldenburg, are given in facsimile. 



Among letters concerning Huygens' principal work, 

 the " Horologium Oscillatorium," we find his well-known 

 letter to Leopold de' Medici of May 1673, protesting 

 against the accusation of plagiarism, which for years 

 caused him a great deal of annoyance. Both this letter 

 as well as Leopold's reply have been printed before, but 

 the editor takes the opportunity of reviewing in a very 

 long footnote the whole question as to the priority of 

 Galileo. The mensurator temporis actually constructed 

 by Galileo was a failure, but in 1641 he gave verbal 

 instructions to his son Vincenzio which resulted in a 

 design of the latter described by Viviani in 1659 in a 

 report to Leopold of Toscana. The editor maintains 

 that a clock can never have been made from this design, 

 or that if made it must have been impossible to make 

 it go, as the wheel would have oscillated instead of 

 rotating ; but this conclusion seems very doubtful, since 

 it depends altogether on the accuracy of the drawing 

 published by Favaro in 1891, from among several 

 existing in the National Library of Florence. In any 

 case it remains an undoubted fact that Galileo was the 

 first to propose the application of pendulums to clocks, 

 that he found the principle of the escapement, and that 

 he only by his age and blindness was prevented from 

 perfecting the invention. The mythical claims of jQOSt 

 Biirgi, so strenuously advocated by Rudolph Wolf, may 

 be safely dismissed,-and that Huygens made the invention 

 quite independently is not doubted by anybody. 



Tiresome questions of priority were always cropping 

 up in the seventeenth century, and Huygens had also to 

 deal with such in the matter of the isochronism of the 

 cycloid. He defended himself against the claims of 

 Hooke and others in a letter to Oldenburg in June 1673, 

 which called forth a dignified reply from the latter, in 

 which he says that English philosophers are not in the 

 habit of attributing to themselves the discoveries of 

 others, but neither will they allow others to deprive 

 them of what is theirs ; many inventive Englishmen 

 have found new truths of which they have spoken freely 

 before printing anything about them, but of late years 

 they have been more careful to preserve their dis- 

 coveries through the medium of the Phil. Trans. 

 Huygens seems to have taken offence at this, as he 

 did not answer for a long time ; and when he wrote 

 again he explained his silence by saying that his letters 

 apparently " ne servoient qu'a me mettre mal avec vos 

 Messieurs dela, les vns ne prenant pas en bonne part la 

 liberty dont j'usois a dire mes sentiments sur leurs 

 ouvrages, et a leur faire des objections, les autres se 

 formant d'autres sujets de mecontentements, ou je n'en 

 attendois point du tout." 



NO. 1503, VOL. 58] 



The last great invention of Huygens dealt with in this- 

 volume is the application of a spiral spring to the balance 

 of a watch. On January 30, 1675, Huygens in a letter 

 to Oldenburg informed him that he had' made a new 

 invention in timekeepers which he announced in an 

 anagram, and a few days later he applied to Colbert for 

 a patent in France for twenty years. The watchmaker 

 Thuret, whom he had employed to carry out the in- 

 vention, gave Huygens a good deal of anxiety by 

 pretending that the invention was his own, or at least 

 was made by him and Huygens jointly ; but after a 

 few weeks he was obliged to give up his pretensions. 

 Eventually, however, Huygens left all watchmakers at 

 liberty to work at the new invention, foreseeing that any 

 attempt to enforce the patent would involve him in- 

 endless lawsuits and expense. A scatter-brained person^ 

 Abbe Hautefeuille, had resisted the granting of the patent 

 on the plea that he had himself applied a straight spring 

 to a clock instead of a pendulum, and that the inventiorv 

 of Huygens was essentially the same thing ! Of more 

 importance was the claim immediately made by Hooke, 

 that he had many years previously made the same 

 invention and that watches had actually been made in 

 accordance with it. How Hooke stuck to his colours, 

 and how he picked a violent quarrel with Oldenburg^ 

 whom he described as "one that made a trade of 

 intelligence" and accused of having betrayed the in- 

 vention to Huygens, all this is well known, and the 

 present volume, in which all the documents are re- 

 printed, does not throw any additional light on the 

 matter. 



In addition to several plates giving photographic 

 reproductions of letters and sketches, the volume con- 

 tains a fine portrait of Huygens and a view of the manor- 

 house of Zuylichem. The very numerous footnotes give 

 ample information about persons and matters referred to 

 in the letters and documents. J. L. E. Dreyer. 



DANTE'S TEN HE A YENS. 

 Dante's Ten Heavens. By Edmond G. Gardner, M.A, 

 Pp. xii -f 310. (Westminster : A. Constable and Co., 

 1898.) 



THE many works in the English language which are 

 being constantly added to the already colossal 

 Dantesque literature are a subject for sincere con- 

 gratulation alike to the country which gave birth to the 

 immortal author of the Divina Comitiedia, and to the 

 English nation. It is, I think, the most conclusive proof 

 of the conspicuous greatness of Dante that his fame 

 should increase in proportion as the era of which he 

 was the first bard and prophet advances in civilisation. 

 " Dante's Ten Heavens," by Mr. E. G. Gardner, is one 

 of the latest contributions to the great subject under 

 discussion, and for the earnest and loving care which the 

 author has evidently devoted to his work he deserves 

 unstinted praise. He has studied a great deal of what 

 has been said about Dante's theological and ethical 

 ideas, and, although Mr. Gardner in his book treats 

 especially of the Paradiso, he often compares similar 

 passages in the three parts of the poem ; so that his 

 work will be of great service to those who are interested 

 in these studies. It is, however, to be regretted that 



