r g THE DEPOSITS OF THE SEA-BOTTOM. 



Section II. 

 The Percentages of the different Sizes of Grains in the Specimens. 



See the charts, pis. Ill and IV. 



Having commented on the amount of carbonic acid, the consistency, and the colour of the speci- 

 mens, and the results of these factors with regard to the classification and the distribution on the 

 the sea-bottom, I shall now pass to the washing and the results obtained by it. That the quanti- 

 tative determination of the different sizes of grains may be justified, will be shown by the fact that 

 the distribution of these grains is subject to a certain conformity to law, which conformity I shall 

 try to show more particularly in the following. 



The manner of proceeding with the washing is the one most commonly used. The specimen is 

 first dried several hours at ioo°, then it is weighed and passed through a sieve the meshes of which 

 had a size of o-5 ram ; the coarser part contains as well calcareous shelis as mineral ingredients. The 

 greater part of the shells are picked off with a pair of tweezers, whereupon the rest is dissolved in 

 hydrochloric acid; and the minerals left are now dried and weighed. The ingredients not measuring 

 .-mm are washed out with cold, diluted hydrochloric acid; the residue is placed in a tall goblet for 

 some hours; when all the ingredients have precipitated, the clear fluid over them is poured off, that 

 the washing shall not take place in water containing too much hydrochloric acid and chloride of calcium, 

 in which the ingredients will precipitate considerably quicker than in pure water. The percentage 

 of the carbonate of lime, which is measured beforehand, is calculated with regard to weight, and from 

 this is got the weight of the ingredients insoluble in hydrochloric acid; and by subtraction is got the 

 weight of the particles smaller than o-5 n ' m . Upon this the specimen is washed in a Schone's washing 

 apparatus with a rate of motion calculated in such a way as to wash out rounded grains of quartz 

 with a diameter smaller than o-02 mm , while the larger grains are retained; although grains of other 

 minerals and of irregular forms precipitate in the water with rates of motion that may deviate some- 

 what from that of the quartz, and although thus by the mentioned rate of motion of the washing 

 many grains over o-02 mm may get away, while some smaller may be left, it has not been possible to 

 pay any regard to this; in the following the two parts produced by the washing, will be designated 

 as the ingredients over and under o-02 mm , and the same will be the case at the other borders. The 

 ingredients over o-02 mm are dried at ioo° and weighed; then the weight of the ingredients under o-02 mm 

 is got by subtraction, while the coarser particles are washed once more and thereby divided into the 

 ingredients over and under o-05 mm . Altogether each specimen is divided into five parts, viz. i) Carbonate 

 of lime, 2) Ingredients over o-5 mm , 3) 0-5 — o-o5 mm , 4) 0-05 — o - 02 mm , and 5) The ingredients under o-02 mm . 



