MISCELLANY. 



253 



and ants will be given to the public before 

 long in a volume of the "International 

 Scientific Series." 



Sea-Sonndings without a Line. Dr. 



Siemens exhibited, at a recent meeting 

 of the London Royal Society, an instrument 

 devised by himself for ascertaining the 

 depth of the sea. In explaining the prin- 

 ciple of this instrument, Mr. Siemens ob- 

 served that the total gravitation of the 

 earth, as measured on its normal surface, 

 is composed of the separate attractions of 

 its parts, and that the attractive influence 

 of dach equal volume varies directly as its 

 density and inversely as the square of its 

 distance from the point of measurement. 

 The density of sea-water being about 1.026, 

 and that of the solid constituents compos- 

 ing the earth's crust about 2.763, it follows 

 that an intervening depth of sea-water must 

 exercise a sensible influence upon total 

 gravitation if measured on the surface of 

 the sea. His instrument, which he calls a 

 bathometer, is described in the London 

 Times as consisting " essentially of a ver- 

 tical column of mercury, contained in a 

 steel tube having cup-like extensions at 

 both extremities, so as to increase the ter- 

 minal area of the mercury. The lower cup 

 is closed by means of a corrugated dia- 

 phragm of thin steel plate, and the weight 

 of the column of mercury is balanced in 

 the centre of the diaphragm by the elastic 

 force derived from two carefully-tempered 

 spiral steel springs of the same length as 

 the mercury-column. One of the peculiar- 

 ities of this mechanical arrangement is, 

 that it is parathermal, the diminishing elas- 

 tic force of the springs with rise of tem- 

 perature being compensated by a similar 

 decrease of potential of the mercury-col- 

 umn, which decrease depends upon the 

 proportions given to the areas of the steel 

 tube and its cup-like extensions." 



The instrument is suspended in such a 

 manner as to retain the vertical position, 

 notwithstanding the motion of the ship, 

 and the vertical oscillations of the mercury 

 are almost entirely prevented by a local 

 contraction of the mercury-column to a very 

 small orifice. The reading of the instru- 

 ment is effected by means of electrical con- 

 tact, which is established between the end 



of a micrometer-screw and the centre of 

 the elastic diaphragm. The pitch of the 

 screw and the divisions in the rim are so 

 proportioned that each division represents 

 the diminution of gravity due to one fathom 

 of depth. Actual experiment has shown 

 the apparatus to be very reliable. 



Formation of Mountain - Chains. This 

 subject is considered by Prof. Joseph Le 

 Conte in the April number of the American 

 Journal of Science, in which interesting 

 facts are presented, the results of obser- 

 vations made by the author in the Coast 

 Range of California. He finds that the 

 actual length of the folded strata is about 

 two and a half to three times the horizon- 

 tal distance through the mountains. It 

 thus appears that from fifteen to eighteen 

 miles of strata, that is, of original sea- 

 bottom, has been crushed or mashed into 

 six miles, with " corresponding up-swelling 

 of the whole mass." 



This diminution of distance, according 

 to the theory of Prof. Le Conte, has not 

 arisen from folding of the strata, but by 

 mashing of them by horizontal pressure. 



From the flattened and elongated form 

 of little nodules of clay found in some of 

 the strata, he concludes that their elonga- 

 tion vertically exactly correlates their short- 

 ening horizontally, and that the one is to 

 the other as two and a half or three is to 

 one. It thus appears that in the compres- 

 sion of the beds their constituent particles 

 underwent a change of form corresponding 

 with the conditions of the pressure. 



These clay pellets or nodules are sup- 

 posed to have been formed on the bottom 

 of gently-flowing streams, are a part of the 

 original sedimentary beds, and are the same 

 in character as those which form greenish 

 spots in slate, as described by Prof. Tyn- 

 dall. 



It will be seen that, in accounting for 

 the elevation of mountain-chains, Prof. Le 

 Conte differs from Prof. Dana in this : that 

 wnile they agree that mountain-chains are 

 formed by yielding of the earth's crust, 

 Prof. Dana attaches importance chiefly to 

 the bending and plication of it, Prof. Le 

 Conte to the crushing of it. He says, " I 

 am satisfied that Prof. Dana greatly under- 

 estimates the amount of elevation by sim- 

 ple mashing as compared with folding." 



