Howell. — On the Radio-activitii of certain Soils. 228 



Art. XXIV. — On the Radio-activity of certain Soils. 

 By J. H. Howell, B.A., B.Sc. 



[Read lu'forc thr Philosophicdl In.stitatf of Cantvrhury, 'ird October, liMKi. ] 



As is well known, radio-active substances are in many cases 

 found present in the water of mineral springs and in the deposits 

 formed by them ; and it has been suggested, since the radio- 

 active products are powerful germicides, that the therapeutic 

 properties of such springs may be due to their presence. In 

 some cases experiments have seemed to show that this is at 

 any rate a partial exj)lanation. An examination of the mineral 

 waters of New Zealand would therefore be interesting ; and 

 with that end in view small quantities of the deposits from a 

 number of the Te Aroha springs were collected. Subsequently, 



in order to get comparative data, the 

 radio - active properties of the light 

 volcanic soil of Mount Eden, Auck- 

 land, of the heavy subsoil of the same 

 district, and also of Parnell clay, were 

 investigated. 



Tlie radio-activity of the Te Aroha 

 deposits was at first tested in a 

 simple electroscope of the following 

 type : — 



The electroscope was charged by 

 touching the head of the screw with 

 an insulated sewing-needle which had 

 been charged by a replenisher, and the 

 rates of leak were determined by a 

 large number of observations taken 

 alternately with and without the de- 

 posit. Although the results seemed 

 on the whole to indicate the presence 

 of radio-active substances, the irre- 

 gularities were too great to allow any 

 definite conclusions to be drawai. It 

 was therefore decided to naodify the 

 apparatus so as to diminish as far as 

 possible any leak over the insulation 

 and also to allow the use of a much 

 larger quantity of the deposit. 



<i, Small brass screw ; l>, 

 plug of sulphur ; c, thin 

 copper wire ; d, gold leaf 

 of about 1 mm. in width 

 observed by a microscope 

 with micrometer eye- 

 j)iece and 1 in. objective ; 

 c, brass cylindrical elec- 

 troscope, 2 in. in diame- 

 ter ; /, glass winflow ; 

 .g, copper cap containing 

 •deposit ; h, earthed coj)- 

 ])er ])late. 



