NA TURE 



[November 28, 1901 



limit the legitimate use of water. In many States and 

 cities either the ice is inspected or the source from which 

 it is obtained, or the local sanitary authority controls its 

 cutting or sale. 



Spitting on the floor of public conveyances or on the 

 side-walks — a dirty habit which creates a nuisance and 

 favours the spread of tuberculosis— is prohibited by 

 regulations which have been very generally adopted. It 

 has, however, been found insufficient to forbid spitting on 

 the floor of conveyances, as it is said that persons seeing 

 such a rule have deliberately spat upon some other 

 portion of the conveyance. A recent State definition of 

 a nuisance (Utah, 1899) is very commendable. A 

 nuisance is " whatever is dangerous to human life or 

 health, and whatever renders soil, air or water impure 

 and unwholesome." The Board of Health of Boston 

 adopted regulations in 1900 for control of the barbers' 

 trade ; inter alia, mugs, shaving brushes and razors must 

 be immersed in boiling water after every separate use 

 thereof; alum, &c., used to stop the flow of blood, must 

 be so used only in powder form and applied on a towel ; 

 the use of powder-puffs and sponges is prohibited : and 

 every barber must cleanse his hands thoroughly 

 immediately after serving each customer. These refine- 

 ments of sanitation must be very difficult to enforce. 



There are excellent reasons why the care of the sick 

 poor should be a part of health department work, and 

 the care of these is in a number of States wholly or 

 partially in the charge of the health department. In 

 most cases it is the outdoor or dispensary work which is 

 given to the health department, but in rarer instances 

 that department also manages the public general 

 hospitals. 



The sweating system is said to be associated with, if it 

 be not the direct cause of, the most terrible phase of 

 human life that is to be found in the United States. 

 The " sweat-shop " is a manufactory in the dwellings of 

 the very poor, among whom, if the home be healthy, the 

 labour reasonable and the wages fair, such work is by 

 no means to be discouraged ; but the conditions of 

 labour are often such as lead to the destruction of the 

 home by the overcrowding and intense application and 

 competition and the starvation wages of the sweating 

 system. American legislation fails, like our own, to 

 bring about any suflicient amelioration of the disease 

 and misery entailed by the sweating system. 



In conclusion, reference may be made to a very useful 

 and full appendix of handbills, forms, notices, &c., used by 

 different sanitary authorities in the United States, which 

 adds much to tlie value of an interesting and important 

 work. 



THE CORRESPONDENCE OF HUYGENS. 

 Oeuvres completes tie Christiaaii Huygetis. Publiees par 



la Socidte Hollandaise des Sciences. Tomeneuvi6me, 



Correspondance 16S5-1690. Pp. 663 + 3 plates. (La 



Haye : M. Nijhoff, 1901.) 

 npHE monumental edition of Huygens' works has now 

 -*- reached its ninth volume, and at least one more 

 will be required to complete his voluminous correspond- 

 ence. When reviewing previous volumes we remarked 

 that many private letters of a non-scientific nature might 

 NO. 1674, VOL. 65] 



well have been omitted, as their insertion is the principal 

 cause of the great extent to which the work has grown ; 

 but this complaint does not apply to the volume now 

 before us, in which there are scarcely any letters which 

 one could wish omitted, as the few which do not treat 

 of scientific matters give interesting glimpses of life and 

 manners. 



In the beginning of 1685 Huygens was still negotiating 

 with the French (lovernment about his return to Paris, 

 and it is not quite clear whether he wanted to go back 

 or not, and whether the revocation of the edict of Nantes 

 was really the sole obstacle. Anyhow, nothing came of 

 the correspondence, and he stayed on at The Hague 

 till the spring of 16S8, when he settled at Hofwijck, a 

 property in the neighbourhood of the city which had 

 belonged to his father (who died in March 16S7) and of 

 which his elder brother, Constantyn, lent him the use. 

 As Constantyn was secretary to the Prince of Orange, 

 his time was naturally much taken up with affairs of 

 State, but he still found time to correspond with his 

 brother on his favourite pursuit of telescope making, 

 until he had to accompany William III. on his memor- 

 able expedition to England in 1688. Several letters give 

 vivid pictures of the great anxiety felt in Holland after 

 the departure of the fleet and the surprise and joy at 

 the rapid progress of the Prince from Torbay to London. 

 The interesting news contained in the letters of Con- 

 stantyn from London inspired Huygens in the summer 

 of 1689 with a wish to renew old acquaintances and 

 make new ones in England, and accordingly he spent 

 more than two months there, associating with Boyle, 

 Halley, Newton (whom he now met for the first time), 

 his old correspondent Duillier and others. The greatest 

 scientific event of the time was, of course, the publication 

 of Newton's "Principia"' two years before. In June 

 1687 Duillier wrote to Huygens from London that some 

 of the Fellows of the Royal Society were much excited 

 over the approaching publication of a new work by 

 Newton, and mentioned shortly some of the subjects 

 dealt with in it. In reply, Huygens wrote that he was 

 longing to see the book and did not object to the 

 author not being a Cartesian, provided he did not 

 make such an assumption as that of universal attrac- 

 tion. No doubt he and Newton must have had some 

 conversations on the subject in 1689, and two memoranda 

 by Newton on motion in a resisting medium probably 

 date from this visit of Huygens to London. They were 

 already published in 1701 together with a few notes 

 written by Huygens in his copy of the " Principia," 

 which after his death was acquired by a certain Groening, 

 who imagined that Newton's memoranda (which are in 

 his own handwriting) were also written by Huygens. In 

 the " Discours de la Cause de la Pesanteur," published 

 in 1690 with the "Traite de la Lumifere," Huygens proves 

 the earth to be an oblate spheroid and explains why the 

 seconds' pendulum is of different length in difterent 

 latitudes. But he assumes that gravity has its seat at 

 the centre of the earth only, and in the appendix (written 

 after the publication of the "Principia') he refuses to 

 admit that all the particles of two or several bodies 

 attract or tend to approach each other, as it seems clear 

 to him that such attraction cannot be explained by any 

 principle of mechanics. And in a letter to Leibnitz in 



