METEOKOLOGY. 



most soft and moist. Where the road had been 

 much disturbed, and over any pool of water, 

 the iris disappeared, and no trace of a bow 

 could be seen elsewhere, on the grass or in the 

 sky. The conclusion drawn was that the sur- 

 face of the mud was thickly covered with glob- 

 ules of pure water, perfectly spherical, and, 

 although resting on the mud, not in absolute 

 contact with it ; but from their invisibility to 

 the eye, these globules must also have been ex- 

 ceedingly minute. 



Soap Bubbles, and the Nature of Cloud. M. 

 Felix Plateau, son of Professor Plateau, being 

 about to throw out from a capsule, or broad, 

 shallow vessel, a slightly viscid liquid, endeav- 

 ored, by throwing it obliquely, to spread it out 

 in a sheet ; the unexpected result was that the 

 film of liquid thus formed instantly drew to- 

 gether at the edges into a hollow bubble of 3 

 to 3 inches diameter, which slowly fell. He 

 chen repeated the experiment many times with 

 soap suds, and always successfully, while now 

 there were usually several bubbles formed at 

 each trial, sometimes as many as fifteen at once, 

 their diameter less as the number increased. 

 He succeeded best with a vessel of basin shape, 

 about 6 inches in diameter, and containing a 

 considerable quantity of liquid 1 part of Mar- 

 seilles soap to 40 parts of water the liquid being 

 thrown out at an angle of about 45 with the 

 horizon, the person turning rapidly round 

 meanwhile, so as to produce as extensive a 

 sheet as possible. Observing from an upper 

 window, while another below performed the 

 experiment, he discovered that the liquid sheet 

 of very irregular form, and indented on the 

 edges, was resolved along the edge into numer- 

 ous full drops, while the remainder of it was 

 generally torn into several parts, each one of 

 which closed up rapidly, so as to form a com- 

 plete bubble. 



It has long been a disputed point among me- 

 teorologists whether clouds are composed of 

 minute solid drops or of almost equally minute 

 hollow spheres or vesicles. Saussure declares 

 that he caught and measured, on the Alps, par- 

 ticles of cloud, the vesicular character of which 

 was unquestionable. The actual lightness of 

 the particles which form even very dense and 

 opaque clouds, and the fact that clouds do not, 

 as do collections of solid drops, show rainbows, 

 have long been instanced in confirmation of the 

 theory of vesicles ; while among the chief ob- 

 jections to it has been the difficulty of conceiv- 

 ing how the vapor, in passing to the liquid 

 state, could aggregate in the form of envelopes 

 enclosing air. Professor Plateau considers 

 that the experiments above alluded to help to 

 solve this difficulty, since they show that the 

 molecules of water need not directly aggregate 

 in the form of vesicles. It is sufficient that the 

 molecules at first unite in open sheets of any 

 figures or curvatures ; each of these will then 

 immediately close, so as to give rise to a vesi- 

 cle. And the formation of the films, however 

 difficult in itself, is more easily conceived than 



the formation at once and entire . of the vesic- 

 ular bodies. 



Question of Formation of Rain near the Earth: 

 Bain Gauges. Since the year 1767, many me- 

 teorologists have come to adopt the opinion 

 that the larger part of the rain which falls on 

 the surface of the earth does not proceed from 

 the clouds, but is derived from the lower 

 strata of the atmosphere, within 200-300 feet 

 of the surface. This paradox arose chiefly in 

 consequence of experiments in which rain 

 gauges placed at moderate elevations in the 

 atmosphere were found to collect much less 

 rain than those placed on the ground a result 

 which will commonly hold true in testing the 

 rain fall with the usual forms of rain gauges 

 and in the ordinary manner. 



Now, it must be observed, that in these ex- 

 periments the higher gauges are placed on the 

 roofs of houses, the summits of church towers 

 or other erections ; and that not only are all 

 these objects which present themselves as ob- 

 stacles to the wind, but that the common form 

 of gauge is itself, though of so much less size, 

 such an obstacle. To determine the effect of 

 such obstructions, Mr. "W. S. Jevons, author of 

 the paper from which this abstract is made, set 

 up at a distance of of an inch apart, two ob- 

 long plates of glass, and causing a current of 

 air continually charged with smoke to ascend 

 between these, he introduced at one side, with- 

 in, a small obstacle to represent a house or 

 gauge : with such an arrangement, it could 

 readily be observed that the moving current of 

 air between the plates, obstructed at the place 

 of the object, rose in a curve over it, and in 

 this part of its course moved more rapidly ; 

 the curves traced by the smoky air in its move- 

 ment being exactly observed, were represented 

 in a drawing ; and the relative velocities in the 

 several parts of the current were also noted. 

 In like manner, when a wind, the movement 

 of which can be taken as in a general way uni- 

 form, meets an obstacle, some parts of it must 

 move more rapidly in sweeping over the latter, 

 just as, also, a river flows most rapidly in the 

 narrowest part of its channel. As parallel 

 facts, a wind is known to be in all cases most 

 fierce at the corners of buildings, the ends of 

 high walls, or on the summits of hills. 



Mr. Jevons considers, that in the facts now 

 given is to be found the whole explanation of 

 the observed deficiency of rain in elevated rain 

 gauges. A falling rain drop is influenced at 

 once by gravity and the motion of the air ; it 

 moves through the diagonal of a rectangle, of 

 which the perpendicular represents the velocity 

 of fall, and the horizontal the force of the wind. 

 If at some fixed point, as the summit of an 

 obstacle to the wind, there occur continually 

 an increase in this horizontal force, the rain 

 drops will at such place be as constantly hur- 

 ried along and spread apart in their course, so 

 that fewer drops (less rain) can there fall on a 

 given surface than will fall where no such 

 interfering cause operates, and a surplus of rain 



