H. A. Tempany 



315 



The arrangement of the cage and support is shown in Fig. 1. 

 The cage and support were suspended by means of a hght vertical 

 metal rod from one end of the beam of a balance placed on a table 

 above, a hole of suitable size being cut in the bottom of the balance 

 case and of the table to permit the passage of the rod. 



The cage and support were enclosed inside an ordinary bell jar 

 standing on a thick ground glass sole, the hght vertical suspending rod 

 passing through the neck of the bell jar ; the neck of the bell jar was 

 closed by two microscope slides in which semicircular nicks had been 

 filed, each of them being of a depth equal to half the diameter of the 

 suspending wire, thus enabhng the two shps to be closed edge to edge, 

 the suspending rod passing through the small opening in the centre. 

 Two other slips of glass were placed so as to cover the juncture of the 



Fig. 1. 



first two. The top and bottom edges of the bell jar were ground and 

 received an ample application of grease so as to make the system tight. 

 Within the bell jar a shallow glass dish was placed containing concen- 

 trated sulphuric acid so that a uniformly dry atmosphere was maintained 

 within the system. 



The tare weight of the cage and support were determined by counter- 

 balancing them with weights on the right hand scale pan of the balance, 

 subsequently the block of soil under observation was introduced and 

 its weight also determined. In making a weighing the shps covering 

 the neck of the bell jar were separated by a distance sufficient to allow 

 the suspending rod to hang freely. The shrinkage was determined 

 by inserting in the upper surface of the block of soil two glass threads 

 which had been drawn o^ to a fine point and coloured red with red ink. 

 These were placed at a suitable distance apart in the block, generally 

 about 5 centimetres, and projected through the slit in the cage; they 

 were of such length that their points were immediately opposite to and 



