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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Nov 



to a glass or Insulating arm, for the purpose of connecting it with an accu- 

 rate support upon which it can move with the greatest facility. In connexion 

 with this arm and disc there is a pencil carried forward to the line of indi- 

 cation. The third disc before stated is fised to a standard at ahout three 

 inches from the first : to this a wire is attached and carried into the earth. 

 By this arrangement the electricity put in motion by a thunder-cloud is re- 

 ceived and registered. The effect during a thunder-storm is extremely inte- 

 resting. When a cloud charged with the electric fluid comes within the 

 range of the conductor, the movable disc begins slowly to pass from the first 

 to the third disc, discharging each time a proportion of the electricity, and 

 increasing in rapidity of motion until the discharge of the cloud by lightning 

 takes place. It then falls hack to tlie first disc, and remains perfectly quiet 

 until the next electric cloud approaches. If, in the interim, a cloud charged 

 with rain only should descend or pass over, no movement of the disc takes 

 place. 



For the pluviometer, at a distance from the outside of the observatory, 

 there is a receiver of one foot square, clear from all surrounding matter that 

 might interfere with the direct fall of the rain upon its surface. From this 

 receiver a pipe conducts the rain into another receiver inside the observatory, 

 directly under the registering apparatus; in this there is an air-float con- 

 nected with a set of inclined planes, each inclined plane being equal to one 

 inch of rain. These inclined planes, as they pass up, move the indicator 

 across the destined proportion of the paper ; showing, as it proceeds, the re- 

 sult of each drop to the hundredth part of an inch in superficies, and con- 

 tinues to advance until it arrives at one inch. It is then instantly discharged, 

 and returns to the zero of the scale, or commencement of another inch. The 

 internal receiver is calculated to contain six inches of rain. 



The evaporator is supplied with water from a vessel which is, in form, an 

 open cube of one foot square, placed by the side of the receiver for rain, and 

 filled from a correct gauge to a given number of inches ; it is covered with 

 a plate of glass, elevated sufficiently above the edge of the vessel to prevent 

 rain from falling into it, but not so close as to prevent the air from freely 

 acting upon the surface of the water. A receiver inside the observatory is 

 placed under the arm of the indicator upon the same level as that outside, 

 connected by a pipe. In this receiver there is a float, governed by the eva- 

 poration from the external vessel, which moves the pencil of indication until 

 an inch of the water has evaporated ; it then, as in the rain-gauge, returns 

 to the zero. This is repeated for several inches until the receivers are nearly 

 empty, when they must he refilled from the external vessel. 



The power or force of the wind is registered by a combination of suspend- 

 ed weights, acted upon by inclined planes or edges in connexion with a board 

 of one foot square to receive the impression ; this board is kept in opposi- 

 tion to the direction of the wind by a powerful vane, its motion being as 

 free from friction as possible, every part being correctly counterpoised. When 

 the board is acted upon by the wind, it raises the suspended vieights by a 

 chain passing over a pulley in a line with the direction of the wind, and well 

 secured from the weather. The suspended weights in connexion with an in- 

 clined lever carries the pencil of indication along the scale, and registers the 

 weight lifted in oz. and lb. avoirdupois. The scale having been found, by 

 repeated trials, to be correctly equal to the weights recorded upon it. The 

 direction of the wind is also registered at the same time by another pencil, 

 which marks the course upon the paper, throughout the whole circle of the 

 horizon, or that proportion through which it passes. 



Section B.— Chemistry and Mineralogy. 

 "On the Decomposition of Water into its constituent Gases by Heat." 

 by W. R. Grove. — Prof. Grove, in the first place, called attention to the 

 fact, proved by Cavendish and the French philosophers, that oxygen and 

 hydrogen being exposed to a high temperature, or the electric spark, im- 

 mediately combined to form water. He theu announced his discovery Ihat 

 all the processes by which water may be formed are capable of decompos- 

 ing water. He believed that the explosion of the mixed gases by the 

 electric spark was due only to the heat of the spark, and not at all to 

 electrolysis. Priestley's method for decomposing gases by passing them 

 through heated tubes was described, and the advantages of using a form of 

 A'olta's eudiometer, in which incandescent platina was employed, to ell'ect 

 decomposition, pointed out. By an apparatus of this kind, ammonia, cam- 

 phor, the prot- and per- oxides of nitrogen were readily decomposed. It 

 was stated that hydrogen gas exposed to the ignited wire always shows 

 the presence of oxygen ; and that it is impossible to pass hydrogen gas 

 through water without its taking up so much oxygen, as to acquire the 

 power of giving luminosity to phosphorus in the dark. It was found that 

 if hydrogen and carbonic acid were exposed to the action of the ignited 

 ■wire, there was a contraction of one volume, leaving a residue of carbonic 

 oxide. If, instead of carbonic acid, carbonic oxide was employed, the 

 mixed gases expanded in volume ; and the carbonic oxide, taking oxyen 

 from the water, was converted into carbonic acid. Here we have two dis- 

 similar results produced by the same cause — by means of hydrogen we take 

 oxygen from carbonic acid, and by means of hydrogen we take oxygen 

 from water. If steam is formed in the eudiometric tube and acted on by 

 the iguited wire on cooling, a small bubble of gas is formed, which is found 

 to be oxygen and hydrogen in the exact proportions in which they form 

 water. This is the result of the first action of the heated wire : — in a few 

 seconds a small bubble of gas is formed, but if the action be continued for 

 a week, it does not increase in quantity. It is, however, easy to remove 

 the bubble as it is formed, and bring a fresh quantity of steam under the 



influence of the heated wire, and thus collect a quantity of gas which 

 should be quite sulficient for any eudiometric examination. Numerous 

 forms of apparatus were described by which this experiment can be per- 

 formed. It might be objected that, as the wire was ignited by a voltaic 

 battery, the decomposition was not due to the heat of the wire, but to an 

 electrolytic action. This objection would not, however, be maintained by 

 those who were acquainted with electrical phenomena. With the view, 

 however, of removing all doubt, the use of the battery was entirely done 

 away with, and all the results were obtained by the agency of heat aloae, 

 in the following manner. Into a silver tube a capillhry lube of platina is 

 soldered, and this is again connected with a bent tube, which admits of 

 the removal of any gas formed. The tubes being filled with distilled 

 water, their ends being immersed in vessels of oil or water, the flame of a 

 spirit lamp, urged by the blow-pipe, is brought to bear upon the capillary 

 tube of platina, by which it is almost immediately brought to a white heat. 

 The water is, of course, instantly converted into steam ; and this steam is 

 decomposed by the agency of the heat alone. By boding, we thus convert 

 steam into mixed oxygen and hydrogen gases ; and this operation may be 

 continued for any length of time by removing the bubble of gas formed, 

 and bringing a fresh supply of steam under the influence of the heated 

 platina. If fused globules of platina are dropped into water, there is im- 

 mediately formed a bubble of oxy-hydrogen gas, which may be collected 

 in an inverted tube. Prof. Grove went on to show the probable connexion 

 between this phenomenon of decomposition and the spheroidal slate of 

 fluids when they are projected on capsules of heated platina, which had 

 been referred to a repulsive action of a coating of steam enveloping the 

 spheroid of fluid ; but in all probability the revolving drop was under- 

 going decomposition by the agency of the heat to which it was exposed. 



Dr. L. Playfair remarked that the facts which Hr. Grove had an- 

 nounced might possibly be regarded as due to a citalytic action of the 

 platina, such as had been observed by Dr. Faraday, and such as was evi- 

 denced in the action of oxi<le of copper on the hypochlorites. Many 

 bodies at high temperatures exhibited a great affinity for oxygen, which 

 they did not possess at lower temperatures, as, for instance, silver, gold, 

 and even platina itself, which metals absorbed oxygen when intensely 

 heated, and gave it out again on cooling. If the experiments had been 

 tried in tubes of quartz or silica, they would not have been open to the 

 objection which the use of so peculiar a metal as platina appeared to 

 involve. 



Dr. Leeson made some remarks, which went to show that in all proba- 

 bility the bursting of steam boilers might be explained by the discovery of 

 Prof. Grove, 



Mr. Hdnt explained some experiments of Woolfe on the boilers of some 

 Cornish steam-engines, which appeared to prove the conversion of steam 

 into gas under the influence of the heat to which the water and steam were 

 exposed in the experiments. 



Prof. Faraday thought Mr. Grove's discovery would not explain the 

 bursting of steam boilers, which might be easily done hy Prof. Boutigny's 

 experiments on the spheroidal condition of fluids. He did not agree with 

 Prof. Grove that the repulsion of the steam was insufficient to explain the 

 spheroidal state. He would rather desire, in the present stage of the 

 inquiry, to discuss the philosophy of the question than the applications of 

 iMr. Grove's discovery. Was it a decomposition of water by the agency 

 of heat, or was it the action of certain substances when heated ? It ap- 

 peared to him that the investigation was a great step onwards and towards 

 a knowledge of the corpuscular action of bodies, and he did not doubt Ihat 

 some remarkable developments as to the influence of caloric in overcoming 

 the force of aggregation would ensue. 



On the changes which mercury suffers in glass ressch hermetically sealed. 



Prof. Oersted read a paper on this subject. He said that the progress 

 of these changes is so exceedingly slow, that it seldom becomes sensible 

 for years. He had observed them twenty years ago in a glass bulb of 

 mercury. At first a yellow powder was formed in the bulb, and after some 

 years a black one. He took up the subject in 1838, experimenting with 

 four bulbs, two of while and two of green glass, carefully weighed, in order 

 to detect any portion of air Ihat may be admitted through the pores or fis- 

 sures of the glass. The weight, however, remained unaltered. In July 

 1839, a small change was visible. At first a feeble ring of yellow powder 

 adhering to the glass was observed, where the mercury had been a long 

 lime in contact with the glass. And again in a new place, under similar 

 circumstances, a new ring was formed, and so on. The surface itself upon 

 n hich the mercury had rested some time had a thin covering of yellow ad- 

 herent powder. In the course of years the yellow powder became black. 

 The mercury had losi a great deal of its fluidity, and it adhered slightly to 

 the glass. The order in which the two colours follow each other indicate 

 Ihat they are not produced by oxidation. In the green bulbs no change 

 was visible. In 184,5, Prof. Oersted procured twelve bulbs, six of which 

 should contain besides the mercury, atmospheric air, the air of the other 

 six being expelled by boiling the mercury; three of each series being 

 while, and three green glass. In July last there was no sensible change 

 in the first series (namely, mercury mixed with air), but in the second 

 (from which the air had been expelled), change had taken place at all but 

 one. Karefaction of the air had no conuexion with the phenomena, but the 

 boiling of the mercury seemed to have some influence upon them. The 

 Professor intends to continue the investigation of these phenomena, which, 

 however, appear to him to depend upon a reaction between the glass and 



