NA TURE 



[March 4, 1909 



much smaller, indicating tlie existence of a still more 

 penetrating type of radiation tiian tlie 7, but our pre- 

 parations are hardly sufficiently active to enable us to 

 establish this beyond doubt. Here again the experiments 

 we propose with the radium 7 rays may throw more light 

 on the matter. 



Frederick Soddy. 



Alexander S. Russell. 

 Physical Chemistry Laboratory, University of 

 Glasgow, February 27. 



The Radio-active Deposits from Actinium. 



In Nature of February 25 there appeared a letter from 

 Prof. McLennan containing the results of some experi- 

 ments recently made by Mr. W. T. Kennedy on the 

 behaviour of the active deposit from actinium emanation. 



So far as may be judged from the details given of the 

 observations, they substantially confirm the results obtained 

 by the writer, which are to be found in the P/ii/. Mag., 

 May and June, 1908. 



The suggestion that the differences in the quantity of 

 active deposit observed on the positive and negative elec- 

 trodes can be explained by the different rates of diffusion 

 of the ions is an interesting one, but it seems likely that 

 the determining factor is the frequency of collision between 

 the active deposit particles and the gas molecules or ions 

 with which they are mixed. 



It is impossible to make a complete comparison between 

 the experiments of Mr. Kennedy and myself until further 

 data are available. S. Russ. 



Physical Laboratories, Manchester University. 



The Production of Prolonged Apncea in Man. 



Noticing the letter by Dr. H. M. Vernon in Nature of 

 February 18 on " The Production of Prolonged Apnoea in 

 Man" it recalled to my mind some observations on the 

 same subject communicated to the Philosophical Magazine 

 in 1833, vol. iii., p. 241, by Michael Faraday, and re- 

 printed in his collected " Researches in Chemistry and 

 Physics," pp. 358-62. 



The effect of a bout of forced breathing in enabling a 

 person greatly to prolong the time during which they can 

 hold their breath was brought under the notice of Faraday 

 by Sir Graves C. Haughton. 



Faraday was ever one who put things to a practical 

 use, and he gives directions as to the mode of proceeding 

 when one had to enter a noxious atmosphere to rescue a 

 person overcome by the fumes of a poisonous gas. Ho 

 says : — " Avoid all unnecessary action ; for activity exhausts 

 the air in the lungs of its vital principle more quickly, and 

 charges it with bad matter. Go collectedly, coolly, and 

 quietly to the spot where help is required : do no more 

 than is needful, leaving what can be done by those who 

 are in a safe atmosphere (as the hauling up of a senseless 

 body, for example) for them to do. 



" Take the precautions usual in cases of danger in 

 addition to the one now recommended [namely, by pre- 

 paring the lungs by several deep breaths]. Thus, in a 

 case of choke-damp, as in a brewer's vat, hold the head 

 as high as may be ; in a case of fire in a room, keep it as 

 low down as possible." 



He concludes his communication with a remark on the 

 effect of increasing the pressure of the air breathed by 

 giving the case in which Mr. Brunei, jun., descended in 

 a diving-bell to a depth of 30 feet below the surface of 

 the water, when it was found that both he and his com- 

 panion could remain under water (by descending from the 

 bell itself) for about twice as long as they could had the 

 air thev breathed only been under normal pressure. It 

 would be interesting to know how long the breath could 

 have been held in the above case had Mr. Brunei employed 

 forced breathing, supplemented by three or four breaths 

 of pure oxygen. If the relation of pressure and time 

 during which the breath could be retained held good for 

 the time of Sm. 135. given by Mr. Vernon, this period 

 should be increased to ifim. 26s. when air under two atmo- 



NO. 2053, VOL. 80] 



spheres (absolute) pressure was breathed, aided by about 

 four breaths of oxygen. W. G. Roval-Dawson. 



40 Creffield Road, Ealing, February 23. 



A Winter Retreat. 



Mr. George Gilbert, a market-gardener in Stonehaven, 

 has shown me a curious phenomenon which I have not 

 met with before, and which, I think, deserves to be re- 

 corded. About the beginning of November a number of 

 children were playing at a tea-party, and they left among 

 the herbaceous plants at the side of the walk an earthen- 

 ware tea-pot, the dimensions of which were 4 inches by 

 3 inches. A few days ago the old tea-pot was discovered 

 lying on its side and without a lid. In the interior, closely 

 packed, were no fewer than thirty-seven of the common 

 garden shelled-snail, and "when ejected they were found to 

 be all alive. They had spent the months in their winter 

 retreat. Probably gardeners know that they can trap 

 snails in some such way ; at all events, one often finds 

 snails in confined spaces and sheltered nooks. Still, the 

 question arises. What led one mollusc to follow the others? 

 Is it the sense of smell? What attracted no fewer than 

 thirty-seven to this old tea-pot, probably a very snug and 

 safe place? Still, there is a danger in being in a crowd. 

 One can imagine how delighted a sea-gull would have been 

 to have discovered this larder of fresh meat ! 



John G. JIcKendrick. 



Priestley and Coulomb's Law. 



In our text-books on electricity I do not remember to 

 have seen Priestley's name associated with the proof of 

 Coulomb's law as derived from the fact that no electrifi- 

 cation can be obtained in the interior of a sphere charged 

 with electricity. 



In the article " Priestley " in the " Dictionary of 

 National Biography " it is stated that Priestley anticipated 

 Coulomb's law, and in looking into the matter I find 

 foundation for the statement in the following paragraph 

 from " The History and Present State of Electricity with 

 Original Experiments," by Joseph Priestley, second edition, 

 1769, p. 711 : — 



" May we not infer from this experiment " (absence of 

 electrification within an electrified cup) " that the attrac- 

 tion of electricity is subject to the same laws with that of 

 gravitation and is therefore according to the squares of 

 the distances : since it is easily demonstrated that were 

 the earth in the form of a shell a body in the inside of it 

 would not be attracted to one side of it more than 

 another." C. J. Woodward. 



Birmingham, February 26. 



Barometric Oscillation. 



In my remark referred to by Mr. Braak (February 18. 

 p. 459) I merely meant the increase of temperature which 

 inevitably occurs when a gas is compressed. The com- 

 pression and warming are simultaneous ; this is shown in 

 the passage of a sound wave where the air is compressed 

 and warmed, and expanded and cooled alternately many 

 hundreds of times in a second. If a barometric change is 

 followed by a change of temperature at some subsequent 

 time the result must be due to other conditions than those 

 to which I alluded. W. H. Dines. 



Life and Letters of Prof. A. Newton, F.R.S. 



I HAVE been invited to write a life of the late Prof. 

 Alfred Newton, F.R.S., of Magdalene College, Cambridge. 

 If any of your readers who have letters or reminiscences 

 or other interesting information about Prof. Newton will 

 be kind enough to communicate with me, I shall be 

 exceedingly grateful to them. I will, of course, under- 

 take to return all letters, &c., to the senders. 



A. F. R. W'OLLASTON. 



Savile Club, 107 Piccadilly, W., March i. 



