258 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August^ 



from the examination of Sir John Ilerschel's liourly observations, " that 

 Brussels is entitled to be considered as a point of comparatively gentle baro- 

 metric disturbance, * * * and may be regarded as in a certain sense &nodal 

 point, where irregularities are smoothed down and oscillatory movement in 

 eener'al is more or less checked, and such movements increase as we recede 

 from Brussels as a centre, especially tovarih the norlh-wesl." The curve of 

 ercatest svmmetrvwas obtained from Kamsgate, the nearest station to I'.rus- 

 sels. As'we pro'cfcd lov-arch the nurlhu-esi, the symmetry is considerably 

 departed from, especially by the greater development of the first subordinate 

 wave on the posterior slope, by which the maximum of the 12tb became 

 superior. This portion of the wave formed a striking contrast to the smular 

 portion in 1845, which was characterised by a considerable depression. It 

 IS not a Utile curious, remarked the author, and goes far to show that we are 

 approaching the true explanation of the nodal character of Brussels to ob- 

 serve that movements so dissimilar in their character, so opposite in their 

 value and presenting themselves under such a diversity of aspects, should, in 

 a certain locality and on particular lines of country, manifest, by means of 

 the barometer, constant and well defined phenomena, that may be recognised 

 year after year, and which give to the curves of barometric rise and fall dur- 

 ing the period of their occurrence a peculiar symmetrical appearance. 2nd. 

 Two Mstems of waves or currents, one having a ijmeral direction of progress 

 fromtiie north-west, the other from the south-west, traversed the area during 

 the period of the great wave. This is the same result to which we were con- 

 ducted by an investigation of the symmetrical wave of 18-12. The relative 

 positions of the individual waves were somewhat diflTeient from those ol the 

 wide bi-dual waves of 1842 ; but there were some striking points of resem- 

 blance The north-westerly svstpni in each case exhibited the largest wave, 

 both as regards amplitude and altitude. The intervals between sinalar phases 

 of north-westerly waves were nearly equal in 1842 and 1846. During the 

 interval that elapsed between transits of these similar phases in 1842 and 

 1846 the same number of south-westerly waves passed over the area— and 

 from the whole it appears highly probable that we have not only ascertained 

 another return of the great symmetrical wave (the sixth) but have also de- 

 tected the return of at least three of the individual waves contributing to its 

 production. 3rd. The very precipitous fall of the barometer characterising 

 the posterior slopes of the north-westerly system, as developed by the dis- 

 cussion of the observations of 1842, is fully confirmed : in connexion with 

 this, the decrease of oscillation from the north-west towards the south-east 

 is also strikingly developed, as on former occasions. The author, in alluaing 

 to the area over which these observations extend, remarked that the British 

 Isles present afar too limited area for the purposes of examining thoroughly 

 thP'^e atmospheric movements ; he observed that in the more extensive ex- 

 amination which the movements of November, 1842, are now undergoing, 

 there are four stations at which the barometric changes are of an opposite 

 character during the first eight days of November,— namely, Christiana and 

 St. Petersburgh in the north, and Paris and Geneva in the south. The curves 

 at St. Petersbumh and Geneva present the most decided opposition; rising 

 at the one while falling at the other. The turning point in each case oc- 

 curred on the 5th. These opposite movements he conceived to be occasioned 

 by the opposite slopes of two waves passing from the south-u-est, and that 

 the half breadth of each wave extended at least from Geneva to St. Peters- 

 burgh. Such being the extensive character of the waves in question, in 

 order to judge them in their totality it will be absolutely necessary to enlarge 

 the area of observation. The centre of Europe is well dotted over with baro- 

 meters, from which accurate results may be obtained ; but even the British 

 Isles, in connexion with that portion of Europe now under observation, form 

 but a small part of the vast space over which the waves themselves extend. St. 

 Petersburgh is an important northern station, from which we have most ex- 

 cellent observations ; but we require them also from Iceland, the northern 

 parts of Norn-ay, Sweden and Lf.pland, and also from Archangel in one di- 

 rection, and from the southern parts of France, from Spain, Portugal, and 

 the northern parts of Africa in the other; also from the Mediterranean they 

 would be highly important. Observations stretching from the most western 

 point of Africa 'to the extreme north of Europe would go far to determine the 

 longitudinal directions of the north-westerly systems of waves. In reporting 

 the general progress of the inquiry, INIr. 15irt slated that we are now in 

 possession of materials for examining the great symmetrical wave, not only 

 in particular years, as 1842, 1845, and lS4C,but also over the central parts 

 of Europe and the dominion of the Kussian empire, as far as Suka, ou the 

 norlh-west coast of America. He has combined observations extending 

 from the west coasts of Ireland and the Orkneys on the one hand, to St. 

 Petersburgh and Geneva on the other; and he apprehends that the whole 

 of the barometric movements over this area, which occurred during the first 

 eight days of November, 1842, are fully explained by the transits of two 

 large waves ou two sets of parallel beds of oppositely directed wiuds— one 

 from the soulh-west, the other from the north-west. The continuation of 

 the investigation will be submitted at future meetings of the Association. 

 In connexion with this, the author observed that a most important point 

 appeared to be developing itself by means of these observations. Those 

 from the north-west appeared strongly to indicate that somewhere in that 

 direction the origin of the great barometric disturbances (a centre of oscilla- 

 tion) giving rise to the waves that pass onwards towards the south-east is 

 to be sought. We have already obtained the nodal point of the two great 

 systems of European barometric undulations— namely, Brussels. Between 

 the Orkneys, which appear lo be the nearest station to the norlh-west cen- 

 tre of oscillation, and Brussels the greatest decrease of oscillation occurs. 



This line of the greatest diminution of oscillation appears to be well deter- 

 mined. The author closed his report with an allusion to the American sys- 

 tem of atmospheric waves, especially those that accompanied the great 

 Cuba hurricane of October, 1844, which has formed the subject of an ela- 

 borate investigation by Mr. M. C. Uedfield, of New York; and was of 

 opinion that the revolving storm, so ably brought to light by iMr. Kedfield s 

 labours, was produced by the crossing of two large long waves moving m 

 different directions, as suggested by Sir John Herschel in his " Ueport on 

 Meteorological Ksductious," presented to the Association in 1843. 

 " On tlie Decomposition of Water" By Dr. Robinson. 

 The afhnity which combines the elements of water is lessened by any in- 

 crease of temperature above that of the atmosphere, up to 202°. If the 

 intensity exerted in opposition lo that of a battery by water during elec- 

 trolysis be measured, and again when the voltameter is healed, it is found 

 to decrease. In the first instance, its measure referred to iny particular 

 standard, as deduced from a mean of 12 sets is 598-9, temperature 61 2'. 

 The next by a mean of 13 gives 



e = 5C7-5 . . . t =: 135° 4' 

 and the third mean of 12 



e = 5310 . . . t =: 201° 2'. 

 Applying lo these the theory of jirobable errors, so successfully used in 

 other branches of science, I find it is more than 10,000 to 1 that the differ- 

 ence thus shown is not all error of observation, and an even bet that it is 

 not 5 wrong. The expression of e is affinity of platinum for oxygen, 

 minus twice that of hydrogen, or 



e := o. p — 2 o. h 

 and from this I compute that o. h changes 232 for 100°. 



This process is confirmed by a difierent process. The forinula for the 

 intensity of zinc and copper excited by dilute sulphuric acid is 



E = o. z — o. cu — o. h 

 In Daniell's cell you substitute o. cu for o. h, and have 



E' = o.z. — 2 o cu. 

 In the latter instance, E' undergoes no change by heating the cell to 163°. 

 The metallic aliinilies therefore do not vary within that range. But in the 

 former E increases by heat, caused by the diminutive of o. h, and it gives 

 the change = 27'9 fur 100°; the mean of all being 251. It is curious 

 that if this rate were uniform, the temperalure of decomposition by heat 

 would be 2386° In these experiments the conducting power of the elec- 

 trolyte is greatly increased by heat. The only objection which I see 

 against this conclusion is, that perhaps these effecls may be due to the 

 action of heat in facilitating the escape of gases. An experiment w^hich I 

 made seems to oppose this. If the apparatus be placed under the air- 

 pump, the removal of pressure should show a similar change. This is not 

 the case : when it is reduced to 1 inch of mercury, the measure of e re- 

 maios unchanged. I think this a very curious result ; it is quite the re- 

 verse of what I expected, for I had supposed heat would exalt these 

 affinities up to a certain point, and afterwards that its action would change 

 character. But its infiuence seems here always an antagonist to aflinity. 

 How then does heat ever produce the combination ? The remark of Davy 

 that hydrogen cannot be made lo buru except by contact with a solid heated 

 sous to be /HHiiHous, makes me conjecture that iigAHs the agent which 

 produces the molecular change of the three volumes of mixed gases into 

 two of steam. 



" On the Precipitate caused in Spring and River TKa/ers by Acetate of 

 Lead." By Prof. Connell. 



Nearly all well and river waters are known to yield a white precipitate 

 with acetate of lead. This precipitate is rarely due to any chloride, as 

 silver salts have too little action to countenance such an explanation ; and 

 its ready solubil.ly in acetic acid shows that it is not caused by sulphates, 

 unless in so far as it is not dissolved by that acid. The ordinary course I 

 have ascertained to be the presence of carbonate of lime ; but the re- 

 markable fact is, that the reaction both of the acetate and of the acetic 

 acid takes place even afltr the water has been boiled and filtered, so that 

 carbonate of lime remains dissolved independently of the presence of car- 

 bonic acid. The waters referred lo yield carbonate of lime when evapo- 

 rated after having been boiled and filtered. To ascertain whence this 

 carbonate of lime has proceeded, I passed a current of carbonic acid 

 through lime water, till the precipitate at first formed was redissolved, and 

 then boiled and filtered the liquid ; but it did not afiect lead salts to the 

 same extent as common waters do. Neither did distilled water which had 

 been left some days in contact with finely pounded marble. I incline to 

 tliink that the origin of the dissolved carbonate of lime is double decom- 

 position between an alkaline carbonate and a soluble lime salt ; and have 

 found, in all waters yielding the reaction, alkalies united to acids. The 

 common water of the town of St. Andrews contains -^^^^ of carbonate of 

 lime after being boiled and filtered. It also contains a trace of carbonate 

 of magnesia, which substance may occasionally be, in part, the cause of 

 the reaction referred to, although lo a far less extent. 



" On the Cause of Evaporation, Rain, Hailstorms, and the Winds of 

 Temperate Regions." By G. A. Howell. 



Mr Kowell stated his opinion that amongst the variety of theories given 

 there is none that will fairly explain all the phenoniena of evaporation. 

 The theory of Dr. Huttun on rain may be thought sufiicient to account for 

 moderate rams, but totally fails when applied to such heavy ram as hat 

 which fell in London, August 1st, last year. Mr. Kowell endeavoured to 

 I show that the phenomena of evaporation, clouds, ram, lightning, hail, ine 



