Howell. — On the Badio- activity of certain Soils. 225 



10'4. On removing the deposit and wiping out the can, the 

 leak due to the influence of the can only was found to be 2 in 

 ten minutes, which gives as leak due to deposit only 84 per 

 ten minutes. The surface of the can had meanwhile become 

 covered by an amalgam with mercury, and it is interesting 

 to note the falling-oi! in the leak due to the can alone. 



Fifth Day. — Can only r5. Deposit replaced, 8-0, 7-3, 8-2, 

 10-0 : average, 8-4. Effect due to deposit only, 6-9, which is 

 less than the effect of the previous day' but greater than the 

 initial effect. 



Volcanic Soils. 



A. Light Volcanic Soil. — For purposes of comparison similar 

 experiments were done "with some of the light volcanic surface 

 soil common in the Mount Eden district of Auckland, an ap- 

 proximately equal volume being taken. 



The leaks per ten minutes obtained over a period of four 

 hours were 12-0, 12-7, 177, 22-0, or an average of 15-9, while 

 those due to can alone were 2*2, 1-8, or an average of 2-0. 



The Te Aroha deposit was placed in the can on the same 

 day, when the leaks were 100, 97, while on the following day 

 the leaks due to the Te Aroha deposit were 9 0, 9 '2, and to the 

 can alone r8. 



The experiments indicate that the light volcanic soil contains 

 substances of greater radio-activity than the Te Aroha deposit, 

 though the explanation of the rapid rise in the rate of leak is 

 not obvious. 



B. Volcanic Subsoil.— ^eyondi the boundary of the light 

 volcanic district, what is locally known as " heavy volcanic 

 soil " is found, and about 10 in. below the surface the volcanic 

 ash forms a very hard " pan," which is attacked better with the 

 pickaxe than with the spade. Some of this subsoil from a depth 

 of about 15 in. was taken, the leak due to the can alone having 

 just previously been found to be 1"5 per ten minutes. The 

 following were the leaks due to the subsoil : 40-8, 380, 400, 40-8. 

 400, 36 0, 49-3, 37-8, 357, 37-2, 450, 450, 367, 400, 417, the 

 average of fifteen readings being 40 '3. 



On the morning of the second day, the subsoil being left 

 undisturbed overnight, the following leaks were observed : 52-5, 

 52-3, 45-5, 517, 567, 467, the average being 509. Later on in 

 the same day the leaks were 57'2, 57-2, 58-2, 55-0, 55-0, 600, or 

 an average of 57'1. 



On the third day, the subsoil still being in the can, the leaks 

 were 52-2, 53-8, 587, 508, 567, or an average of 54-4. 



8— Trans. 



