378 



NA TURE 



[September 16, 1922 



be, so far as possible, free from errors arising from 

 unknown changes in liquid-air areas and from the 

 unknown solid-air and solid-liquid tensions. It will 

 be seen that the capillary-rise method in reality does 

 this, though there is difficulty in measuring the 

 internal bore and keeping it clean. But the following 

 arrangement seems to be as nearly as possible free 

 from these objections, and to be adapted to measure 

 the tensions of interfacial liquid surfaces as well. 



The liquid (mercury excepted) is made to drop 

 from a fine capillary tube having thin walls as in 

 Fig. 1. In forming the drop, it spreads upward over 

 the exterior surface and reaches a limiting size, shape, 

 and position. It then slips down the tube at a uni- 

 form velocity with little modification in size or shape, 

 and after suffering a slight check in its motion breaks 

 its connexion and falls. We may then equate the 

 whole tension about the tube with the weight of the 

 drop, so that T, a Xir^ e = W L or T 1o = Wl/t^„ where 

 T !a is the liquid-air tension and d, is the external 

 diameter of the tube. 



The same drop formation occurs when the tube is 

 arranged to drop water downwards in any lighter oil, 

 or by a bent tube (Fig. 2) upwards in a heavier oil. In 



W„ Pv-Po 



this case we have the equation T„ =^f-x — ", 



wd, p w 



where the suffixes w, 0, e, and i denote the words 

 water, oil, external, and internal, and p is density, 

 from which the tension of the water-oil surface may 

 be calculated. 



On the contrary, when oil is dropped either down- 

 wards or upwards in water, it does not spread on any 

 exterior water-glass surface, but forms its attachment 



as in Fig. 3. In this case we have T. 



wdi 



Po 



These all give results agreeing with those recorded 

 in the standard tables. 



In accordance, then, with this conception of an 

 elemental force not included in the class of " attrac- 

 tive " forces, we should expect that these changes 

 in area would be always attended by a rise in tempera- 

 ture. If it be asked why the enveloping area about 

 a free molecular mass tends to decrease, there is no 

 answer ; and neither is there an answer to the question 

 as to why a large mass tends to approach another. 

 Wilson Taylor. 

 Physics Laboratory, 

 University of Toronto, Canada, July 15. 



The Influence of Science. 



The seeming contradiction in my summary account 

 of the case of Galileo (Nature, August 5, p. 180), to 

 which Sir Oliver Lodge directs attention in his letter 

 (Nature, August 26, p. 277), needs an explanation. 

 The great work of Copernicus (1543) was dedicated 

 to a Pope, Paul III. ; none of the Roman Congrega- 

 tions found any objection to it, and (Whewell, " His- 

 tory of the Inductive Sciences," I. 418, ed. 1847), 

 says " lectures in support of the heliocentric doctrine 

 were delivered in the ecclesiastical colleges." This 

 was because of its being taught as a purely scientific 

 doctrine. 



Sir Oliver writes that Galileo " had endeavoured to 

 get the Church to realise that the doctrine was not 

 realty antagonistic to Scripture when reasonably in- 

 terpreted." This statement needs qualifying. Had 

 Galileo contented himself with teaching the Coper- 

 nican doctrine as a scientific hypothesis, he would 

 not have been molested. But, being a fierce con- 

 troversialist, he wanted to confound his many ad- 

 versaries, the mathematicians, and the Aristotelians, 

 by showing that Scripture was on his side (cp. Sir 

 David Brewster, " Martyrs of Science," p. 58). Hence, 



NO. 2759, VOL. I IO] 



disregarding the advice of the Bishop of Fermo " not 

 to raise the question," and that, too, of many other 

 ecclesiastical friends, among them Cardinals and 

 Prelates, to the same effect, he demanded that " the 

 Pope and the Holy Office should declare the Copemican 

 system to be founded on the Bible." Hincillae lacrymae. 

 On the other hand, the attitude of the Churchmen is 

 well illustrated in a letter from Cardinal Bellarmine 

 to the Carmelite friar, Foscarini, one of Galileo's 

 friends, dated April 12, 1615. He writes : " If a true 

 demonstration should be found that the Sun is placed 

 at the centre of the world, and the Earth in the third 

 heaven, and that the Sun does not turn round the 

 Earth, but the latter round the former, then it will 

 be necessary to proceed with great prudence in the 

 explanation of Scripture, which seems to say the 

 contrary, and rather to avow that we have not 

 understood it, than to declare a demonstrated fact 

 false." Astronomers had to wait until the discovery 

 of aberration by Bradley before such a true demon- 

 stration was found. 



Sir Oliver also writes that " Galileo was made to 

 recant, to abjure, and curse the theory of the earth's 

 motion." Whewell tells us (loc. cit., p. 419), " He 

 (Galileo) was accused before the Inquisition in 1615, 

 but at that period the result was that he was merely 

 recommended to confine himself to his mathematical 

 reasonings upon the system, and to abstain from 

 meddling with Scripture." After his contempt of 

 court, in the second trial, of the year 1632, he was 

 condemned as " vehemently suspected of heresy." 

 He was sent to Arcetri, and had to recite a penance 

 of certain prayers. 



There was ho implication in my former letter, as 

 Sir Oliver writes, " that there was really no punish- 

 ment, and that there was no call for anxiety and 

 distress." The implication was that his troubles were 

 largely, if not entirely, of his own seeking, and that 

 his treatment was, according to the quotations I gave 

 from Whewell, and from De Morgan, comparatively 

 mild. I purposely quoted from non-Catholic writers, 

 as they cannot be suspected of partiality towards the 

 Roman Congregations. To these I add the testimony 

 of Sir David Brewster (loc. cit, p. 88) : " During the 

 whole of the trial Galileo was treated with the most 

 marked indulgence." Sir Oliver Lodge's quarrel is, 

 therefore, with such eminent scientific men as Whewell, 

 De Morgan, and Brewster (see also op. cit, p. 77), to 

 whom we may add Huxley, who (" Life and Letters," 

 ii. 424) avowed that " the Pope and the Cardinals 

 had rather the best of it." 



But my chief implication was, and is, that the case 

 of Galileo cannot fairly be considered as evidence of 

 the hostility of the Church to natural science, and as 

 a hindrance to her legitimate influence. Finally, I 

 trust Sir Oliver Lodge will not think me discourteous 

 in not treating of the other points raised in his letter, 

 as I do not consider them to be relevant to the present 

 discussion. A. L. Cortie, S.J. 



Stonyhurst College Observatory, 

 August 31. 



The Production of a Standard Source of Sound. 



I have recently had occasion to consider the 

 problem of constructing a simple standard source of 

 sound, and have been favourably impressed by the 

 possibility of emploving a " hot wire " grid — as used 

 in the Tucker microphone (Phil. Trans. A, vol. 221, 

 pp. 389-430) — for this purpose. In this microphone 

 the grid is made of fine platinum wire and heated by 

 a current of 20-30 milliamperes. It is mounted in 

 the orifice of a Helmholtz resonator, and when the 

 latter is stimulated by a sound of suitable pitch, the 

 vibration of the air in the orifice causes an increase 



