29 



Washing analyses. 



In order to get an exact idea of the mechanical constitu- 

 tion of the samples, they were all subjected to a washing pro- 

 cess by the aid of Schöenes's washing apparatus and were 

 sifted from the coarser ingredients. 



First the ingredients larger than O.s'"™ were separated off 

 by means of a sieve ; these were then again sorted by the aid 

 of coarser sieves, the meshes of which measured 1, 2, 4, 8°^"" 

 and so on. As these particular samples are for the most part 

 very rich in coarser ingredients, the sorting of these is of the 

 greatest importance in the examination of the mechanical con- 

 stitution. It is especially on this, that conclusions with regard 

 to ice transport and a great many other circumstances are based. 



It is important to notice that the accuracy of the percen- 

 tages, which can be estimated by sifting, decreases, as the size 

 of the grains increases. 



The percentages for the grains of more than 8^^ can 

 only be stated approximately, as only a very limited number of 

 these grains will be found in a sample of about a hundred 

 grammes, which is the amount that has usually been at our 

 disposal for this purpose. But a slight accident during the 

 hauling up of the material may cause a greater or lesser 

 number of stones to get into the sounding tube and affect the 

 result very considerably, so that the graphical representations 

 will also everywhere show great irregularities on the outermost 

 right side of the curve. If an exact determination of the 

 amount of these ingredients is to be made one would require 

 to have a very great quantity of each sample, and then still 

 larger ingredients, the determination of which would also be 

 very inexact, would enter into the samples. On the other hand 

 the percentages for the ingredients from 05 to H^'^ are exceed- 

 ingly accurate. 



