1847.] 



THE CIVIL ENGINEER AND ARCHlTECrS JOURNAL. 



S59 



■winds of temperate regions, and storms of lower latitudes, may be fairly 

 explained by Ihe hypothesis he submitted; i.e. electricity having uo 

 ■weight and diffusing itself equally over the surface of bodies, the minute 

 particles of water, even in their most condensed state being completely 

 enveloped in their natural coating of electricity, occupy, together ivilh 

 their electricity, nearly the space of an equal weight of air, and are thus 

 rendered sufliciently buoyant to be carried away by the wind ; but that 

 ■when expanded by heat their specific gravity being then reduced, and their 

 capacity for electricity being increased by the increase of surface, they are 

 then buoyed up into the air by their electrical coatings ; that when the 

 rising particle is condensed it becomes surcharged by the contraction of its 

 surface; if this takes place near the surface of the earth, the surcharge 

 escapes and the particles fall as dew ; but if it is condensed when above 

 the electrical attraction of the earth, it is still buoyed up by the electricity, 

 and on the escape of the surcharge, the particles attract each other and 

 form clouds and rain. Hills aud mountains cause clouds and rain by con- 

 ducting the electricity from the vapour, and not by condensing it ; and on 

 these grounds he again suggests, as a test of the theory, the experiment 

 he proposed to the British Association in 1840, i. c. " To cause rain by 

 raising electrical conductors to the clouds by the aid of balloons." In 

 support of the proposition he read an extract from a letter he received 

 from Mr. W. H. Weeks, of Sandwich, dated Dec. 2", 1812, in which that 

 gentleman assures him that " It has several times happened that when his 

 electrical kite has been raised immediately under a distended, light, fleecy 

 cloud at a moderate elevation, and a free current of sparkx has passed from 

 the apparatus for some ten or twelve minutes, he has suddenly found him- 

 self bedewed with a descent of fine misty rain, and on looking up has 

 seen the cloud upon which he was operating surprisingly reduced in mag- 

 nitude." Electrical kites cannot reach Ihe clouds, aud can only be raised 

 in windy weather, when the clouds must be every instant passing away 

 from the influence of such apparatus ; aud if they have such effects, what 

 may we not anticipate from the use of conductors which would reach the 

 clouds, and could be raised in calm weather? ^Ir. Rowell considered that 

 from the reduction of temperature at the height of the clouds, the vapour 

 in those regions must be always condensed, but invisible from being so 

 diffused ; and that the formation of clouds is not owing to condensation, 

 but to the escape of electricity allowing the particles of vapour to attract 

 each other. In support of these views, and also to show that the ascent 

 and support of vapour at great heights must depend on some agent which 

 is independent of heat or cold, he exhibited the table following — 



„ . , , Temperature 'Water heavier 



""S""' of Air. tliaa Air. 



Level of the Sea . . . . +60° . . . . 860 times. 



1 mile +43 .. .. 1,083 „ 



2 miles -f26 .. .. 1,303 „ 



Smiles +9 •• •• Ij^IS ;> 



4 miles — 8 .. .. 2,160 „ 



Smiles —25 .. .. 2,719 „ 



Another cause of rain is the pressure of the particles of vapour upon 

 each other; for if a cloud be of great depth, say the lower part one mile 

 high and the upper part two miles, as the electricity of the particles would 

 be equal, those in the upper part would not have sufficient for their sup- 

 port, and would therefore press downwards, and those in the lower part 

 would have more than enough to support them at that height, and would 

 therefore press upwards, aud thus press the particles in the middle of such 

 cloud into contact and form rain, while the electricity being pressed out of 

 the cloud, would accumulate on the surface till it could force its way to 

 the earth or other clouds, and thus cause lighining. Violent hail-storms he 

 attributed to the sudden equalization of the electricity of large masses of 

 Tapour floating at diflerent heights in the air, and brought by currents and 

 ■various circumstances the one over the other. The dirterence between the 

 lowest mass and the top of the upper mass of clouds may amount to two 

 or three miles. The violence of storms in such cases depends upon the 

 density of the clouds and the height of their upper strata : as, the greater 

 the height at which the hailstones begin to form, the greater will be the 

 degree of cold they will acquire, and consequently the more powerfully 

 they will act in freezing the vapour with which they come in contact 

 during their fall ; the greater also they will become by the accumulation 

 of vapour in falling ; and the greater will be the velocity with which they 

 arrive at the earth. The lightning accompanying such storms may be 

 caused by the lower clouds forming conductors for the electricity from the 

 highly-charged upper clouds to the earth. The diminution of the pressure 

 of the atmosphere previous to and during rain, he ascribed to the escape 

 of electricity from the invisible vapour or clouds; thus causing a vacuuui 

 or rarefaction in the regions of the clouds: and the air from its elasticity 

 rising to till the space, decreases the pressure on the mercury. Allowing 

 that the trade winds, land and sea breezes, &c., are caused by changes of 

 temperature, yet he contended that the more irregular winds are owing in 

 a much greater degree to the fall of rain and the escape of electricity from 

 the cloud, than to any change of temperature; for as each panicle of 

 water to be buoyant must, together with its electrical coating, occupy the 

 space of au equal weight of air, as water is 860 limes heavier than air at 

 the level of the sea, every particle of water that falls to the earth must 

 have occupied 860 times more space when suspended in the air ; theiefore, 

 if in a given time one inch of rain falls to the earth, it must, during that 



time, have caused a vacuum or rarefaction in the space above to the extent 

 of S60 inches: the vacuum would in fact be greater than this, for vapour 

 to be buoyant must occupy a greater space according to its elevation ; but 

 as the density of the air decreases according to the elevation, the effect 

 must be the same, *. e. for every inch of rain that (iills the vacuum would 

 be equal to the gradual abstraction of the whole of the air to upwards of 

 70 feet in height over the whole district where the rain falls; which rare- 

 faction must be filled up during the time the rain is falling by a rush of air 

 from the surrounding districts, although such wind may not always be felt 

 in the same locality in which the rain falls. He supports his views by 

 referring to the storms of wind which swept over England from the north- 

 west and west last autumn, at which time France and other parts of the 

 continent were deluged with rain. He exhibited the following table of 

 heavy rains (mentioned by Prof. Forbes in his Report on Meteorology in 

 1840) to show that they are suflicient to account for violent storms ; and 

 had no doubt that if we had accurate accounts of the extraordinanj rains 

 which sometimes fall within the tropics, they would be found sufficient to 

 account for the most tremendous hurricane : — 



Place. 



Date. 



Depth of Rain 

 iu inches. 



Time. 



Averape Vacu'im per aq. 

 mile per second. 



Calskill, U.S. July 26, 1810 .. 18in. .. 7^ hours. 



Genoa Oct. 25, 1822 .. 30in. .. 24 „ 



Joyeuse .... Oct. 9, 1S27 .. 31in. .. 22 „ 



Geneva .... May 20, 1827 .. 6iu. .. 3 ,, 



Gibraltar . . Nov. 27, 1820 . . 33 in. . . 26 „ 



Naples .... Nov. 22, 1826 .. -^ in. .. 37 minutes 



Perth Aug. 3,1829 .. | in. 



30 



1,331,908 cub. ft. 



693,733 „ 



782,027 „ 



1,109,973 „ 



704,406 „ 



809,980 „ 



887,978 „ 



" TAe Progress of Tides." — The Mastek of Trinity College, Cam- 

 bridge, delivered a report of a Committee consisting of himself and Capt. 

 Sir .1. Ross appointed at Southampton to draw up a plan for a naval expe- 

 dition for completing our knowledge of the progress of the Tides. 



The knowledge which we possess of the tides, looking at the connectioa 

 of the phenomena over the whole surface of the ocean, is extremely im- 

 perfect at present, and not at all likely to be completed in any material 

 degree in any finite time, by the observations which voyagers mainly di- 

 rected to other objects will supply. The coasts and islands which sur- 

 round or break the waters of the Pacific, are especially the seats of this 

 ignorance. We know the time of tide near Cape Horn, but cannot trace 

 the progress of the tide waves along the western coast of South and North 

 America. AVe know the time of tide on the coasts of New Zealand, but 

 cannot connect this fact with the rise and fall of the water on the coasts of 

 the smaller islands in the centre of the ocean. We know the tide hour on the 

 eastern coast of New Holland, but cannot trace the progress of the tide 

 to the PhiUippines or to the coast of China — though some observations of 

 Admiral Liitke, made a few years ago, supply a valuable addition to our 

 knowledge on this subject- The course of the tide wave among the 

 islands of the Indian Sea is likewise entirely unknown. Observations 

 made by voyagers mainly guided by other purposes appear unlikely 

 to supply this deficiency in our knowledge, for even when made with 

 sufficient care and for several weeks at detached places, they are rarely 

 connected with each other or with neighbouring places. It does not 

 appear that while we are thus left to depend on chance for our tidal know- 

 ledge, we shall ever be able to know from observation whether the tide 

 wave in the Pacific does or does not move from east to west. But a ship 

 sent out on purpose to observe the tides could very soon ascertain a great 

 body of facts of this kind. The observers would, of course, observe the 

 facts of the tides in connection with each other; and would arrange their 

 plan of operations so as to extend their lines of connection from knowa 

 points to unknown. By such a mode of proceeding the co-tidal lines for 

 every part of the Pacific and Indian Oceans might probably be drawn 

 (oiniiting the minor details in the interior of archipelagos, &c) in a year, 

 at most in two years. 



The tide observations made, at the request of Dr. Whewell, in 1834, for 

 a fortnight by the coast guard on the coasts of Great Britain and Ireland, 

 prove how great an accession our tidal knowledge may receive from con- 

 nected observations ; and still more those made in June 1835, for a fort- 

 night along the coasts of the whole of Europe and the eastern coast of the 

 United States of North America. By means of these observations the 

 general course of the tides in the year thus explored has been determined. 

 If an expedition were sent for the purpose of making tide observations, it 

 would not be at all necessary to have, as in the instances just mentioned, 

 simultaneous observations along the whole line of sea observed. It would 

 suftice to connect a few places by corresponding observations, in some 

 cases for a fortnight, in others for a few days ; then, to connect one of 

 these places with others, and thus to proceed through the whole region 

 observed. It appears by the experience of the surveys which we have 

 referred to that the observations may be made by sailors, such as those 

 employed on the co^st guard, under proper directions. On those occasions 

 the necessary apparatus was speedily constructed by the persons employed. 

 It might, however, be useful also to employ, in several places, self-regis- 

 tering tide-gauges such as are already established in several Euglisli 

 ports. 



We conceive that the project contemplated by the Association in ils 

 recommendation is very desirable ; and might best be attained by sending 

 out a vessel which should have for the object of its voyage to make tide 



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