TRANSACTIONS OF SECTION A. 537 



per Lour. If emission of heat at this rate goes on for little move than a year, or, 

 say, 10,000 hours (13i months), we get as much heat as would raise the tempera- 

 ture of 900,000 grammes of water by 1° C. It seems to me utterly impossible that 

 this can come from a store of energy lost out of the gramme of radium in the 

 10,000 hours. It seems to me, therefore, absolutely certain, that if emission of 

 heat at the rate of 90 calories per gramme per hour found by Curie at ordinary 

 temperatures, or even at the lower rate of ."JS found by Dewar and Curie from 

 a specimen of radium at the temperature of liquid oxygen, can go on for month 

 after month, energy must somehow be supplied from without to give the energy 

 of the heat getting into the material of the calorimetric apparatus. 



I venture to suggest that somehow ethereal waves may supply energy to the 

 radium while it is giving out heat to the ponderable matter around it. Think of 

 a piece of black cloth hermetically sealed in a glass case, and sunk in a glass vessel 

 of water exposed to the sun ; and think of another equal and similar gluss case 

 containing white cloth, submerged in an equal and similar glass vessel of water, 

 similarly exposed to the sun. The water in the former glass vessel will be kept 

 very sensibly warmer than the water in the latter. This is analogous to Curie's 

 first experiment, in which he found the temperature of a thermometer, with a little 

 tube containing radium kept beside its bulb, in a little bag of soft material, to be 

 permanently about 2°C. higher than that of another equal and similar thermo- 

 meter, similarly packed with a little glass tube not containing radium beside its 

 bulb. 



By observing the temperature of the water in our two glass vessels, a calori- 

 metric investigation might be made, showing how much heat is given out per hour 

 by the black cloth to the surrounding glass and water. Here we have thermal 

 energy communicated to the black cloth by waves of sunlight, and given out .ns 

 thermometric heat to the glass and water around it. Thus we actually have 

 energy travelling inwards through the water in virtue of waves of light, and out- 

 wards through the same space in virtue of thermal conduction. 



My suggestion respecting radium may be regarded as utterly unacceptable, but 

 at all events it will be conceded that experiments should be made comparing the 

 thermal emission from radium wholly surrounded with thick lead with that found 

 with the surroundings hitherto used. 



'■[Si' 77Ji?7' die in der Afmosjjluire loid im Erdhoden enfhaltene radioactive 

 " ■ Emanation. Von T. Elster u. H. Geitel. 



Wir beehren uns der British Association hiermit eine kurze Uber.sicht der 

 Ergebnisse von Versuchen vorzulegen, deren Gegenstand die, wie es sclieint, 

 allgemein verbreiteten radioaktiven Eigenschaften der natiirlichen atmosphiirischen 

 Luft und gewisser Bestandteile des Erdbodens bilden ; sie beweisen in ihrer 

 Gesamtheit die Existenz einer radioaktive7i Emanation in der Atmosphare, die, 

 wenn nicht ausschlie.islich, so doch zu einem wesentlichenTeileausdemEvdkiJrper 

 herstammt. Eine Mitteilung dariiber diirfte im Zusammenhange mit der heutigen 

 Diskussion iiber die Natur der aktiven Emanationen vielleicht niche ohne Interesse 

 sein. 



Die Versuche bezogen sich : 



1. Auf den Betrag der inducierten Aktivitiit, die man auf einem beliebigen 

 Leiter (am besten einem Drahte von unveranderlicher Liinge) dadurch erzeugt, 

 dass man ihn eine gemessene Zeit lang in freier Luft zu einem bestimmten Potentiale 

 negativ geladen halt. 



2. Auf Vergleichung des Gehaltes an radioaktiver Emanation in der an 

 verschiedenen Orten im Erdboden enthaltenen Luft. 



3. Auf die radioaktiven Eigenschaften der mineralischen Bestandteile des 

 Erdbodens selber. 



In Betreff des ersten Gegenstandea haben wir gefunden, dass die unter gleichen 

 Bedingungen dutch die freie Luft inducierte AktivitatinderNahederMeereskiiste 



