September 26, 1912] 



NATURE 



in a concise, and not too technical a form, the 

 leading' characteristics and details of modern 

 road construction, and the results of the traffic to 

 which these roads are subject. The relative 

 merits of macadam, granite sets, asphalt, and 

 wood paving- are fully dealt with. 



The author considers that macadam on a good 

 foundation, for horse-drawn vehicles, is the best, 

 and the condition of these roads is greatly im- 

 proved, both as to cleanliness and endurance, 

 when the surface is sprayed with tar ; that 

 creosoted soft wood, such as red pine or yellow- 

 deal, gives more satisfactory results for urban 

 traffic as regards wear than the harder woods, 

 such as oak or jarrah ; that wood paving has 

 the advantage of being silent and not slippery ; and 

 that for motor traffic asphalt paving is the best. 

 The relative endurance, and the time the surface 

 V. ill last without replacing, is given as two years 

 for macadam laid on a good foundation ; for soft 

 creosoted wood paving laid on concrete, fifteen 

 years ; and for rock asphalt on concrete, twenty 

 years. 



Statistics are given showing the great advan- 

 tage that is derived from the use of tar for spray- 

 ing macadam roads, both in the prevention of 

 dust and by increasing the length of the life of 

 such roads, which the author calculates at 33 per 

 cent. It is also shown that the use of motor 

 vehicles reduces considerably the amount of 

 refuse that has to be removed from the surface 

 of the roads. 



The book contains eleven chapters dealing with 

 a general introduction on modern road construc- 

 tion ; macadam roads ; wear of roads ; effect of 

 traffic; tarring macadam roads ; methods of using 

 tar and bitumen; rollers and rolling; paving; cost 

 of maintenance of roads ; with appendices giving 

 a specification for road-making ; wood paving ; 

 tarring ; and copies of the Road Board specifica- 

 tion for pitch. 



HISTORICAL GEODESY. 

 Grandeur et Figure de la Terre. By J. B. J. 



Delambre. Ouvrage augmente de notes, de 



cartes, et public par les soins de G. Bigourdan. 



Pp. viii+402. (Paris: Gauthier-Villars, 1912.) 



Price 15 francs. 

 " T ES conquetes passent, et ces operations 



1 J restent," was the compliment with which 



Napoleon accepted from Delambre a copy of his 

 "Base du Syst^me metrique decimal." The 

 publication of this work of the great French 

 geodesist offers a good reason why the second 

 half of the above remark was as true as 

 the first. The manuscript which Delambre left 

 unpublished at his death gave an interesting- his- 



No. 2239, VOL. go] 



torical account of the pioneer work of the 

 eighteenth century in investigating the size and 

 shape of the earth, and it also reveals the value 

 of his own share in that work. Names well known 

 outside the world of astronomy appear in the book : 

 Colbert gave the first order for a measure of an arc 

 along the meridian of Paris; Robespierre signed a 

 document expelling Lavoisier, Laplace, Coulomb, 

 and Delambre, with others, from the Commission 

 des Poids et Mesures. Many other French names 

 also occur in the book to remind the world how 

 much geodesy owed in its earliest stages to the 

 .\cademie des Sciences. 



The direct effect on contemporary scientific work 

 of such a tremendous upheaval as the French 

 Revolution is well shown in Delambre's account of 

 the delays caused by his repeated arrests at the 

 hands of ignorant provincials. One is tempted to 

 wonder whether, if the metric system had been 

 established at a time when more friendly relations 

 existed between France and England, this country 

 would also have adopted it. M. de Talleyrand's 

 invitation to the British Parliament to appoint a 

 commission of Fellows of the Royal Society to 

 cooperate with members of 1' Academic des Sciences 

 in fixing natural and invariable units of weight 

 and length, is still of more than academic interest. 



Enough has been said of the historical side of 

 this book. It must now be added that Delambre's 

 accounts of the surveys of arcs in the different 

 parts of the world are marked by very close study 

 of all available sources of information. Where 

 possible, the original manuscripts were studied, 

 and by very acute criticism the faults of much of 

 the earlier work and some of the later work were 

 elucidated. Several investigators, notably J. 

 Cassini, come in for pretty severe treatment; 

 Delambre's critical remarks may still be most 

 useful to warn the young observer as to faults 

 to be avoided. The accounts of the journeys of 

 some of the surveying parties are very interest- 

 ing, in particular the journal of the Abbd Outhier 

 on the Lapland survey of 1736. Curiously interest- 

 ing, too, it is to see new items of knowledge 

 gradually entering in as factors in elucidating the 

 problem under discussion. Thus the first emer- 

 gence of spherical trigonometry and the modifica- 

 tion of results owing to the discovery of nutation, 

 come upon the present-day reader with a curious 

 sense of shock. 



.A debt of gratitude is owing to M. Bigourdan 

 for his work in editing the manuscript. We note 

 only one misprint; Groombridge is spelt wrongly 

 on p. 314. The successful way in which the 

 editing has been done may be taken as a sign of 

 the pleasure that M. Bigourdan has felt in carry- 

 ing through the undertaking. 



