SCIENTIFIC SUMMARY. 
309 
barium, containing 52 grms. to tlie litre of water j a solution of carbonate of 
soda, containing 26-5 grms. of tliis salt to tbe litre of water ; a solution of 
sulphuric acid, containing 20 grms. of strong sulphuric acid to the litre 
of water. These solutions agree among each other, drop by drop. The ad- 
vantage claimed for this method is the non-necessity of having to wash out 
the sulphate and carbonate of baryta, and also the advantage that titration 
does not take place in a fluid rendered turbid by therein-suspended sulphate 
of baryta, which alwavs tends to render the observation of colouration of 
litmus more difficult. 
GEOLOGY AND PALEONTOLOGY. 
The Sediment of Rivers . — This is a subject which, much as it has 
been studied, still affords room for abundant research, as may be seen 
by referring to the Geological Magazine for April. In this journal 
there is a paper of much interest by the Pev. J. D. De la Touche. The 
author recently made a number of experiments in the river Onny which flows 
by his house. The following is an abstract of these : — 1. A tolerably 
straight and uniform reach of the river was chosen, and along the bank 
100 feet were measured and marked by pegs driven into the ground. Here 
a marked post was erected in the water, to take the height of the flood from 
time to time. This was done every day after any considerable fall of rain, 
and at the same time the rate at which the centre of the stream moves was 
ascertained, by counting with a watch the number of seconds any floating 
substance takes to pass the measured 100 feet. 2. An accurate section 
of the river was made by sounding. From these data the number of cubic 
feet of water which pass this point in a given time could be calculated, 
by knowing the ratio of the speed of the centre to the mean velocity of 
the whole stream. An able practical engineer, who had had much experience 
in this matter, stated that is represented by the fraction four-fifths. But it 
seemed to the author that this rule can hardly be very accurate, and that it 
would be desirable to find the mean velocity by the use of a current metre, 
working in different parts of the section. However, this element once de- 
termined, it is of course only necessary to multiply the area of the section in 
feet, by the mean velocity in feet for a given time, to ascertain the number of 
cubic feet which flow past in that time. 3. The proportion of sediment 
held in suspension was ascertained by collecting a certain measure of water 
(a quart bottle answers the purpose very well), and tlien decanting and 
filtering it. If the filter be carefully dried and weighed, before and after 
the experiment, the difference gives the weight of mud from which the per 
centage of grains to ounces of water can be obtained. Thus there are 
supplied sufficient data to determine how much solid matter passes down the 
river in a given time at any flood. 4. Besides these observations, the 
rainfall at different points of the watershed of the river should be carefully 
registered. Thus some correlation between the two could probably be as- 
certained, so that from year to year an average rate of the wear and tear of 
the surflice of the land might be obtained. 
The Geology of Alaska. — The/ollowing is an extract fl*om a letter ad- 
