August 8, 1907] 



NA TURE 



549 



(6) Though oui- modern bards call each of the solstitial 

 quarter days an Alban, there is very little authority for 

 such a use of the name. What appears likely is that 

 Alban became a name of the midsummer festival, and 

 that a bardic scribe at first wrongly applied the name to 

 the other quarter days. The Alban of the bards covered 

 three days, and each day is specially named. The first 

 is the \'igil of the .\lban, the second is the Alban itself, 

 and the third is the Banquet of the Alban. 



(4) Why have the Welsh made so much of the name 

 .Mban? The reason may be found in the association of 

 the name with Caerleon-upon-Usk. 



(a) There are some ruins near that ancient city still 

 called Mount St. Alban 's. 



(fc) Mr. Wade-gvans has made out a good case for 

 localising Alban's martyrdom at that spot (in " Archjeo- 

 logia Cambrensis, " about two years ago). 



(c) Geoffrey of Monmouth tells us of a great observatory 

 or school of astronomers in or near that city. 



St. Alban's Day being the chief day of the year, and 

 an observatory bearing his name, probably, at Caerleon 

 being apparently the Greenwich of Wales at one time, it 

 is no wonder that the Welsh bards have adopted the name 

 as a solstitial epithet without ever a mention of Alban's 

 jiiartyrdom. 



We have in Wales a very modern instance of the same 

 process. In some districts June 22 is observed as Gwyl 

 Barna, the Vigil of Barnabas. St. Barnabas's Day is the 

 nth, and in the seventeenth century it coincided with the 

 solstice; but since 1752 it has been in those parts associated 

 with the 22nd, and Gwyl Barna is now a name of the 

 solstice. In the neighbourhood of Llandeilo Talybont, 

 Glam., it is the custom of the farm labourers to get 

 together the hay-making implements on the morning of 

 Gwvl Barna, before going to a solstitial fair in the 

 neighbourhood. John Griffith. 



Llangynwyd, Glam. 



The Sun's Motion with respect to the i^ther. 



So far as I know, it has not been pointed out that the 

 velocity of light, as deduced from the observed times of 

 occultation of Jupiter's satellites, is affected to the first 

 order by the motion of the earth and Jupiter with respect 

 to the sether. Taking the times best suited to such 

 observations, when the distance between the two planets 

 is very nearly a maximum or a minimum, there will be 

 no appreciable relative velocity in the line of centres, and, 

 to a first approximation, the velocity with which light 

 from Jupiter approaches us is then made up of the true 

 propagation-velocity increased by the common velocity- 

 component of the two planets in the direction earth to 

 Jupiter. 



In order to determine the sun's motion with respect to 

 the aether, the values for the apparent velocity of light 

 deducible from the observed times of occultation might be 

 analysed, so as to discover any systematic differences 

 depending on the direction of the line of centres. Only 

 very small corrections would be needed on account of 

 the motion of the planets in their line of centres relatively 

 to the sun. The probable absolute error in the finally 

 deduced velocity of the sun (relatively to the ?ether) would 

 be of the same order as that affecting the finally deduced 

 velocity of light. The quantity to be determined might 

 perhaps be swamped by the errors of observation, but 

 even so a superior limit could be assigned to the sun's 

 velocity through the rether. Two of the three rectangular 

 components of that velocity being measured in the plane 

 cf the ecliptic, the determination of the third component 

 would unfortunately be very badly conditioned. It may 

 be some consolation, however, to reflect that a knowledge 

 of our motion with respect to the ;ether is not theoretically 

 unattainable. 



.'\gain, if the mean lethereal density is either less or 

 greater where atomic matter is present than in free 

 fether, it appears from some results which I have lately 

 obtained in connection with a modified theory of gravita- 

 tion that motional forces would be experienced (for 

 example) by two bodies movin." with uniform translational 

 velocity through the aither. These forces would be pro- 

 portional to the product of the masses of the two bodies, 



NO. 197 1, VOL. 76] 



to the square of the velocity of translation, and inversely 

 to the fourth power of the distance between the bodies. 

 They would be equal in magnitude and opposite in direc- 

 tion, but would not in general act in the same line, so 

 that an elongated body, partaking of the earth's diurnal 

 and orbital motion, would in general be acted on by a 

 couple. This couple would vary as the diurnal motion 

 changed the orientation of the body, and if the variations 

 were measurably great, we should have the means of 

 determining, .save for a constant factor and an ambiguity 

 of sign, the velocity of the earth with respect to the 

 sther at any point of its orbit. Observations at three 

 or more points of the orbit would enable us to evaluate 

 the constant factor and to remove the ambiguity of sign, 

 thus determining the velocity of the sun with respect to 

 the a^ther. 



The effects referred to might or might not be detect- 

 able, but by means of quite simple apparatus they could 

 be tested for with great delicacy. I hone shortly to publish 

 a fuller account of the analysis on which the above con- 

 clusions are based. C. \'. Burton. 



Cambridge, July 29. 



The Dos;'s Sense of Direction of Pound. 



Our dog, Spot, of the intelligence of which an 

 instance has been recorded in Nature, is peculiarly 

 sensitive to sound. The following instance may be worth 

 recording. On Sunday, July 21, a heavy storm of thunder 

 and lightning with rain broke over Wick. I sat in the 

 porch of our house watching — Spot with me. The 

 lightning was frequent, and the thunder played round in 

 ail directions — over Bath six miles to the east and Bristol 

 six miles to the south-west. 



Spot barked at each clap or rumble and rushed for- 

 ward, always ioiuatds the direction from which the 

 thunder appeared to come ; the lightning affected him in 

 no way. It was laughable when the thunder appeared to 

 come from no definite direction, but to play round us. 

 For then he ran, barking, over the lawn and round the 

 trees as if angered by a sound he could not locate. 1 

 observed carefully what he did for perhaps half an hour, 

 and I think Spot located the directions of sound at least 

 as quickly as I did myself. F. C. Constable. 



THE INTERNATIONAL CONGRESS ON 

 SCHOOL HYGIENE. 



THE second International Congress on School 

 Hygiene was opened on Monday last at the 

 University of London by Lord Crewe, in the presence 

 of a large gathering, which included delegates from 

 all the countries of Europe, the Colonies, and North 

 and South America, in addition to representatives of 

 administrative bodies in Great Britain. We shall 

 publish at a later date an account of the proceedings 

 of the Congress, but are pleased meanwhile to direct 

 attention to the warm interest taken by the King in 

 the objects for the consideration of which tlie con- 

 gress was convened; indeed, but for the King's inter- 

 vention, the congress would probably have been 

 anything but a success, as will be seen by the opening 

 remarks of the president. Sir Lauder Brunton, F.R.S. 

 Lord Crewe, Lord President of the Council, in opening 

 the congress, said the first duty he had to perform in 

 connection with the opening ceremony was a very agree- 

 able one. He had a gracious command from the King 

 to express to them the interest with which His Majesty 

 regarded the subjects with which that congress was con- 

 cerned and his hopes that its discussions might be a great 

 .success. His Majesty had further commanded him to 

 express his regret that, owing to his enforced absence 

 from London, he was unable to receive those who were 

 to attend the congress. He was also privileged as a 

 member of the Government to express the same desire on 

 their part that the proceedings of the congress might be 

 crowned with success, and on behalf of the Government 

 to offer them all a hearty welcome. It was not in a strict 

 sense an official conference. It was not subject to official 

 control, it was not run on official lines, and it was not 

 subsidised by official money. That, from many points ol 



