April i6, 1908] 



NA TURE 



56: 



dates are not given where they are of importance, and 

 even so well-known a worker in the field as Har- 

 graves is practically ignored. 



The illustrations are numerous, and, on the whole, 

 are verv good; of special interest is the photographic 

 reproduction of a " double deck " Lilienthal machine 

 in flight, which appears to be of the type used by the 

 late Herr Lilienthal on the occasion of his last flight, 

 when he unfortunately met with his fatal accident. 

 Of the great variety of " birds' eye " photograplis 

 given, perhaps the most interesting are the cloud 

 studies given in Figs. 125, 143, and 185; also a fine 

 view of the pyramids of Egvpt, Fig. 200. 



The chapters on ballooning entitled " Ballooning 

 as a Sport," " Scientific Ballooning," and " Balloon 

 Photography," in addition to those on " Military Bal- 

 looning," make interesting reading, and constitute the 

 most useful and trustworthy portion of the book ; there 

 is much information collected in pages devoted to these 

 chapters that might be sought for elsewhere in vain. 

 The account, however, is essentially of a popular 

 kind; it is difficult to read these chapters without 

 raising an "aeronautical appetite"; the description 

 of over-sea ballooning and the illustrations of the 

 de la Vaulx deviaior are particularly interesting. 



Lilienthal on his flying machine. From " Airships Past and Presen 



It is when departing from the declared intention of 

 the work that its author most laj's himself open to 

 criticism. Thus, on p. 17, in discussing the theory 

 of the ascension of the Montgolfiere, there is a 

 simple little pitfall into which the author has gratui- 

 tously precipitated himself. On the assumed baro- 

 metric pressure of 30" of mercury, it is stated (we may 

 presume correctly) that the weight of a cubic foot of 

 air heated to 212° F. is 0059 lb. Herr Hildebrandt 

 then goes on to say : — 



" At a height of S330 feet, a cubic foot of air at a 

 temperature of 32 deg. Fahr. weighs only o'o59 lb., 

 and therefore a ' Montgolfiere ' cannot reach a 

 greater height than this, seeing that the lift then 

 disappears, unless the temperatures, given in the above 

 table, can be e.xceeded." 



The assumption made here seems to be that the air 

 within the balloon does not expand as the pressure is 

 relieved by altitude, just as if the air inside the balloon 

 were contained by a hermetically sealed pressure-proof 

 envelope. 



On p. 30 a description is given of an aneroid 

 barometer which certainly is a mistake; cither the 

 word tube has been used in translation instead of 

 diapl'.ragm, or else the author describes a particular 



N"0. 2007, VO' . 77! 



aneroid (probably made by Bourdon, of Parisi instead 

 of the aneroid as generally constructed ; the almost 

 universal practice of instrument makers is to employ 

 a flexible diaphragm, not a tube as stated. 



On p. 89 it is somewhat puzzling to find that 

 most of the " dirigibles " have a greater content than 

 that of their containing cylinder — according to the 

 figures given. For example, a balloon 30 feet in dia- 

 meter and 148 feet long is given as holding 137,500 

 cubic feet of gas ; in view of the fact that a cylinder 

 ol these dimensions has a volume of only 105,000 cubic 

 feet, this requires some explanation. Several other 

 cases are equally incomprehensible. 



On p. 96 the year 1862 is assigned to Phillips's 

 " Venetian blind " captive machine; this appears to be 

 an error of about thirty years (antedate). 



The fatal accident to Herr Lilienthal is stated to 

 have been due to a want of adjustment, the machine 

 turning over at a height of 50 feet from the ground. 

 The authority for this version of the accident should 

 be stated; the account, as published in Nature (Sep- 

 tember 3, 1896), contributed' by Prof. Carl Runge, 

 from the evidence of an eye-witness (the assistant of 

 Herr Lilienthal), made no mention of any error of 

 adjustment, but attributed the capsize to a sudden 

 gust, which carried the machine to a height of 30 

 metres (100 feet), from which the fatal plunge took 

 place. 



In the chapter on carrier pigeons an account 

 of certain experiments, stated to have been made with 

 trained swallows, is given, but again no trustworthy au- 

 thority is mentioned. A passage may be quoted as 

 follows : — " An Antwerp trainer sent up some swallows 

 and pigeons at the same time at Compiegne, in 

 France. The pigeons covered the distance of 145 miles 

 in 3j hours, while the swallows arrived in i hour 

 7 minutes ; the spaed of the latter was therefore three 

 times that of the former." Now the time taken by 

 the pigeons appears to denote that there was no wind 

 of consequence, and therefore the velocity of flight of 

 a swallow may be calculated as 130 miles per hour, a 

 conclusion full of improbability. Statements of this 

 kind should only be inserted in a serious work after 

 careful verification, and with the authority stated, 

 place and time also being given, if possible. 



NOTES. 



The fourth International Congress of Mathematicians 

 was opened at Rome on Monday, April 6, in the presence 

 of King Victor Emmanuel II., and the proceedings con- 

 cluded on Saturday last, when an invitation was accepted 

 to hold the congress of 1912 at Cambridge. The number of 

 members shows a considerable increase on that of previous 

 congresses, and a great deal of valuable work has been 

 done in the sections. The Guccia medal has been awarded 

 to Prof. Francesco Severi, for his papers on the geometry 

 of algebraic surfaces. We hope to give an account of the 

 proceedings of the congress next week. 



It was announced at the meeting of the Institution of 

 Naval Architects on April S that the council had grate- 

 fully accepted an offer from Mr. A. F. Yarrow, vice- 

 president of the institution, to defray the cost, up to 

 20, cool., of an experimental tank for research purposes 

 to be erected at the National Physical Laboratory, pro- 

 vided that cost of maintenance for the first ten years was 

 assured. A committee is to be appointed to carry out the 

 scheme. Papers on the employment of the steam turbine 

 for various classes of ships took a prominent place in the 

 proceedings of the meeting. Lord Cawdor was elected 

 president of the institution upon the retirement of Lord 

 Glasgow. 



