1848."] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



311 



Atmospheric Waves. 



" Report on Atmospheric Waves." By Mr. Birt. 



The report consists of three parts : — The tirst denoting the information we 

 now possess relative to such waves as have been determiaed : the second 

 treating of the barometric curves which result from the crossing of the 

 Eorth-westerly and south-westerly waves, the two principal systems 

 common to Europe — the most prominent subject being that particular 

 curve known as the "great symmetrical wave of November:" and the 

 third embodying the results that have been obtained during the last year 

 illustrative of the symmetry of the " great wave," more particularly the 

 locality of greatest symmetry and the departure from symmetry in certain 

 directions. Under the second head, the author has thrown together the 

 result of bis inquiries into the forms presented by the barometric curves at 

 certain stations, and has devoted attention to the symmetrical curve of 

 November as it has been observed at the Observatory at Greenwich in the 

 years 1841 to 1845. In connection with this subject, the author remarked 

 " it has been assumed that the symmetrical wave of November consists of 

 Jiee subordinate waves giving rise to the five maxima which characterise 

 it, the central maximum forming the apex of the symmetrical curve, the 

 remainder being subordinate thereto. (" Association Reports," 1846, 

 p. 125.) Upon a close inspection of the curves of the " great wave" as 

 laid down from the Greenwich observations, six subordinate maxima can 

 be traced, three on each side the central apex, which in all the years is by 

 far the most prominent. The mean curve leads to the conclusion that 

 Greenwich is not the point of greitteit sijmmetnj, its closing portion being 

 depressed more than two inches below the commencement. The next 

 feature is the decided rise of the mercurial column during a period of 

 sixty-eight hours preceding the transit of the crest : the value of this rise 

 is "7 inch or about -010 inch per hour. The fall is not so precipitous; the 

 barometer appears to be kept up in this locality by the Jirst subordinate 

 maximum succeeding the crest, so that at the epoch of sixty-eight hours 

 after transit the value of the reading is more than 2 inches higher than at 

 sixty-eight hours before transit. At eighty hours after transit a precipitous 

 fall commences, which continues during the next twenty-four hours, the 

 mercury sinking "36 inch or about '015 per hour. The fall afterwards con- 

 tinues with two slight interruptions, answering to the subordinate maxima, 

 until the close of the wave 148 hours after transit." The peculiar features 

 of the mean curve, especially the difference between the initial and 

 terminal readings, '241 inch, combined with certain features exhibited by 

 the " great wave" at its last return, has suggested the possibility of ex- 

 pressing numerically the departure from symmetry for any station that 

 may be selected. This departure from symmetry is strikingly manifested 

 by the observations of 1846, especially as we proceed from Brussels, the 

 European nodal point, towards Ireland and the north-west of Scotland, 

 and is well seen in the series of curves illustrating the author's report in 

 the last volume of the " Association Reports." Three principal maxima, 

 characterise these curves on the 5th, the 9lh, and the 12th of November ; 

 and the differences of altitude between those of the 5th and 12th have 

 been employed to indicate the deviation from symmetry in the direction 

 already alluded to. The discussion of these differences and the results 

 deduced from them form the third part of the report. The author has laid 

 down on a map of the British Isles these differences, and from them con- 

 structed a chart of the lines of equal deviation from symmetry : these 

 lines range from -lOO inch — which passes north-west of the Channel 

 Islands, proceeds towards the Isle of Wight, skirts the shores of Sussex 

 and Kent, and passes through Ramsgate — to -550 inch, which passes 

 through Limerick, is slightly curved as it crosses Ireland, and proceeds 

 nearly in a straight line across the Scottish Islands to the north-west of 

 Great Britain. The values of these lines express the depression of the 

 maximum of the 6th below that of the 12th. Among these lines the 

 author regards the direction of that representing ■2()0 inch as the best de- 

 termined. It appears to have passed near and to the west of Helstone, 

 this station exhibiting a deviation of -258 inch ; it then proceeded along 

 the coast of Cornwall and Devonshire, crossed the Bristol Channel, entered 

 Wales, and continued its course across Glamorganshire towards Brecon, 

 which it left to the north-west as it rather abruptly changed its direction 

 and proceeded towards Gloucester, which it passed through. It appears 

 to have undergone considerable inflection as it traversed the central parts of 

 England, rising again towards Nottingham, which is removed -025 inch 

 from it to the west : it finally left the shores of England at the south- 

 eastern angle of Yorkshire and entered on the German Ocean. The 

 author solicited attention to a feature which characterises all these lines, 

 especially the one just traced, viz., the decided inflection they undergo as 

 they pass over the land. The chart exhibits two systems of inflection, one 

 being peculiar to Ireland and England ; the general direction of the lines 

 undergoing a change as the line of greatest symmetry is approached, the 

 inflection being governed apparently by the masses of land : and the other 

 to Scotland, the inflection being very decided over the land northward of 

 the Frith of Forth. From the single instance discussed by the author, the 

 result appears to be that the symmetry of the barometric curve is departed 

 from in a greater degree at inland stations, a greater difference between 

 the points selected being exhibited at such stations than at the sea coast 

 on either side. The report closed with some remarks on the non-per- 

 sistency of the direction of these lines of deviation from symmetry, and 

 on the high probability that they revolve about the nodal point of the two 

 principal systems of atmospheric waves, Brussels. 



Health op To-vtns. 



" Report on the Air and Water of Towns." By Dr. Smith. 



In commencing his report the author says, it has long been believed that 

 the air and the water have the most important influence on our own health, 

 — and superstitions have therefore constantly attached themselves to recep- 

 tacles of the one and emanations of the other. The town has always 

 been found to differ from the country : this general feeling is a more deci- 

 sive experiment than any that can be made in a laboratory. The author 

 proceeds to examine all the sources from which the air or the water can 

 be contaminated. The various manufactures of large towns, the necessary 

 conditions to which the inhabitants are subjected, and the deteriorating 

 influences of man himself are explained. If air be passed through water 

 a certain amount of the organic matter poured off' from the lungs is to be 

 detected in it. By continuing this experiment for three months. Dr. 

 Smith detected sulphuric acid, chlorine, and a substance resembling im- 

 pure albumen. These substances are constantly being condensed upon 

 cold bodies, and in a warm atmosphere the albuminous matter very soon 

 putrifies and emits disagreeable odours. The change which this substance 

 undergoes by oxidation, &c., is next examined, — and shown to give rise to 

 carbonic acid, ammonia, sulphuretted hydrogen, and probably other gases. 



The ammonia, generated fortunately from the same sources as the sulphu- 

 retted hydrogen, materially modifies its influences. The consequences of 

 the varying pressure of the atmosphere have been observed ; and it is 

 shown that the exhalations of sewers, &c., are poured out in abundance 

 from every outlet when the barometric pressure is lowered. By collecting 

 the moisture of a crowded room by means of cold glasses and also dew in 

 the open air, it was found that one was thick, oily, and smelling of per- 

 spiration, capable of decomposition and production of animalcules and 

 confervas, — but the dew beautifully clear and limpid. Large quantities 

 of rain-water have frequently been collected and examined by Dr. Smith ; 

 and he says, — I am now satisfied that dust really comes down with the 

 purest rain, and that it is simply coal ashes. No doubt this accounts for 

 the quantity of sulphites and chlorides in the rain, and for the soot, which 

 are the chief ingredients. The rain is also often alkaline, — arising probably 

 from the ammonia of the burnt coal, which is no doubt a valuable agent 

 for neutralising the sulphuric acid so often found. The rain-water of 

 Manchester is about 2J° of hardness, — harder, in fact, than the water 

 from the neighbouring hills which the town intends to use. This can only 

 arise from the ingredients obtained in the town atmosphere. But the most 

 curious point is the fact that organic matter is uever absent, although the 

 rain be continued for whole days. The state of the air is closely con- 

 nected with that of the water: what the air contains the water may 

 absorb — what the water has dissolved or absorbed, it may give out to the 

 air. 



The enormous quantity of impure matter filtering from all parts of a 

 large town into its many natural and artificial outlets, does at first view 

 present us with a terrible picture of our underground sources of water. 

 But when we examine the soil of a town we do not find the slate of 

 matters to present that exaggerated character which we might suppose. 

 The sand at the Chelsea Waterworks contains only 1-43 per cent, of 

 organic matter after being used for weeks. In 1827 Liebig found nitrates 

 in twelve wells in Giessen, but none in wells two or three hundred yards 

 from the town. Dr. Smith has examined thirty wells in Manchester, and 

 he finds nitrates in them all. Many contained a suprising quantity and 

 were very nauseous. The examination of various wells in the metropolis 

 showed the constant formation of nitric acid ; and in many wells an en- 

 ormous quantity was detected. It was discovered that all organic matter, 

 in filtrating through the soil, was very rapidly oxidized. The presence of 

 the nitrates in the London water prevents the formation of any vegetable 

 matter, — no vegetation can be detected, even by a microscope, after a long 

 period. The Thames water has been examined from near its source to 

 the metropolis, and an increasing amount of impurity detected. 



In the summary to this report. Dr. Smith states that the pollution of air ia 

 crowded rooms is really owing to organic matter and not merely carbonic 

 acid, — that all the water of great towns contains organic matter, — that 

 water purifies itself from organic matter in various ways, but particularly 

 by converting it into nitrates, — that water can never stand long with ad- 

 vantage unless on a large scale, and should be used wheu collected or as 

 soon as filtered. 



Steam Navigation. 



" On the Imprerements which have been made in Steam Nasigation." 

 By Mr. Scott Russell. 



The first great improvement that had been made was in the boilers. For- 

 merly, the boiler-flues were constructed of great length, so that the smoke 

 was kept winding round and round in the flues and at last was allowed to 

 escape with difliculty. Now, however, they had adopted the plan of 

 getting as much fire as possible in the shortest space of time, — and this 

 had been accomplished by imitating as nearly as they could the locomotive 

 engine boiler, by having tubes of thin metal which would evaporate a 

 much greater quantity of water in the same time as flues of the usual 

 thickness ; now, also, instead of taking the smoke a long dance as in the 

 old fashion, they used short flues of four to six feet in length, and by having 

 a great many of as thin metal as possible they heated the greatest quantity 

 of water, and had the additional advantage of keeping the metal cool, — 

 in conse^eoce of which a boiler of smaller extent and surface was of 



