268 M. R. Schneider on the Equivalent of Manganese. 



in general a course line passes from inunit to immit through a 

 single intervening knot which is a point of maximum elevation 

 on the course line ; it need not be considered as an exception 

 when, as is frequently the case, the course line arrives at the 

 sea-level contour line without previously reaching an immit. It 

 is to be noticed that a ridge line or a course line may commence 

 and terminate at one and the same summit or immit, and thus 

 form a closed curve. 



The ridge lines, as above defined, determine the watershed. 

 In the case of an isolated conical or dome-shaped mountain, and 

 in general when the contour lines are all of them closed curves, 

 there is no definable watershed ; but in the case of a chain of 

 mountain summits, the watershed runs from summit to summit 

 through the heads of the passes over the connecting cols, i. e. it 

 is made up of a series of ridge lines each extending from a sum- 

 mit to a summit through an intervening knot. And the course 

 lines are, as nearly as may be, the beds of the streams which flow 

 from the heads of the passes down the lateral valleys. The ridge 

 line and the course line respectively are, I believe, the so-called 

 ligne de faite and ligne de thalweg. 



2 Stone Buildiugs, W. C, 

 July 20, 1859. 



XLI. On the Equivalents of Manganese and Nickel. 

 By R. Schneider*. 



THE equivalent of manganese has been hitherto taken as 

 27-56 (or 344-66 for = 100). This number is derived 

 from two experiments of BerzeUust^ in which vi'as determined 

 the amount of chloride of sdver precipitated by a solution of 

 silver from a known quantity of anhydrous subchloride of man- 

 ganese. The results of the two experiments were as follows : — 

 Quantity of subchloride Chloride of Equivalent of 



of manganese employed. silver found. manganese. 



4-20775 9-575 344-631 



3-063 6-96912 344-736 



Inasmuch as in this determination the disadvantageous cir- 

 cumstances occurred which I have mentioned in another place J, 

 attending the employment of metallic chlorides for the estima- 

 tion of equivalents, and as the importance of the equivalent of 

 manganese makes it desirable that it should be deduced from a 

 more numerous series of experiments, a short time ago I in- 

 duced M. Rawack to perform such a series of experiments in 



* Translated by Dr. Guthrie from PoggendorfF's Annalen, No. 8, 1859, 

 pp. 605, 616. 



t Pogg. Ann. vol. xviii. p. 74. Berzelius, Lehrbuch, vol. iii. p. 1223. 

 X Poggendorflf's Annalen, vol. ci. p. 388. 



