"This maximum is found to occur about ten or eleven o'clock P.M. The air will now go on contracting more and more slowly, until about daylight, when it will be at rest, and the barometer will again be at a mean.

"This theory was given by me to the Journal of the Franklin Institute, and published ten or twelve years ago.

"I ventured in that paper to predict, notwithstanding some alleged observations at St. Bernard's Hospital to the contrary, that it would be found by more careful observations that the morning maximum fluctuation would be greater in lofty situations, on the sides of mountains, provided they were not very lofty, than on the plain below.

"For it is manifest, that there will be not only a reaction at these lofty situations, (a little less, it is true, than below,) but some of the air will be lifted up, by the expansion of the air below, above the upper place of observation; which would in all probability more than compensate the diminished reaction at moderate elevations.

"This prediction has been entirely verified by Lieutenant-Colonel Sykes's observations in India, and this verification may be considered as a strong proof of the correctness of the theory. It is quite probable, that maximum day fluctuation occurs later at considerable elevations than on the plain below.

"The theory would lead us also to suppose, that at very great elevations, where the reaction is very minute, only two fluctuations would be found in the day: the maximum at about two o'clock P.M., when most air would be above the barometer; and the minimum at daylight in the morning, when least air would be above it; but I know of no observations to confirm or refute these deductions."

Mr. BALL brought under the notice of the Academy the fact, that the ordinary sturgeon of the Dublin markets is an undescribed species. He stated that Mr. Thompson, of Belfast, and Professor Agassiz, concurred with him in this opinion, and he proposed to call it Accipenser Thompsoni, purposing, if permitted, to give figures and full descriptions in a future number of the "Proceedings."

The Archbishop of Dublin made some observations on a remarkable meteor, lately seen in different parts of Britain.

December 14.-Dr. Apjohn read the following notice, by George J. KNOX, Esq., of "some Improvements in the Voltaic Pile."

"The chief imperfection in the voltaic pile-its want of a constant uniform power of long duration, by which it is rendered almost useless as an instrument of research-having been overcome by the ability of Professor Daniell, the only thing that remained to render it efficient seemed to be, to increase its power; a desideratum accomplished by Mr. Grove, by substituting for copper and sulphate of copper, platinum and nitric acid.

"The following experiments were undertaken with the intention of estimating the relative values of the different constructions of Grove's battery, recommended by Mr. Knight, of Foster Lane, as

far as respects the arrangement of the zinc and platina plates, when, to my surprise, I found the same quantity of electricity to be evolved when the zinc is bent so as to expose an opposing surface to each surface of a platinum plate, as when a platinum plate, of the size of the former zinc, is similarly placed with respect to a plate of zinc of the same size as the former platinum, affording an economical method of arranging a Wollaston's battery, the zincs being bent round the coppers, in place of the coppers round the zincs.

Experiments with Grove's Battery.-The acid solutions were those recommended by Mr. Grove, i. e. pure nitric acid, in contact with the platina; sulphuric acid + 4.5 water by measure, in contact with the zinc. The surfaces of zincs immersed were 3 by 2.5 inches; those of the platina, bent round the porous vessel holding the zincs, were 6 by 2.5 inches. The glasses containing the acid, &c., were 3.2 inches long, 1.5 broad, 3.5 deep. The length of the porous vessel of pipeclay was 2.5 inches, the breadth 0·3, the depth The number of alternations was five.

3.5.

"The porous vessel was found filled with sulphate of zinc, which stopped the action of the battery.

"Second Experiment. The zinc plates being of the same size as the former platina, and the platina of the same size as the former zincs; the zincs bent round the platina; all other things being as before.

"Third Experiment.-Another battery, the diameter of the cells of which was 21⁄2 inches, gave a diminution of only one-half of the quantity of gas after the lapse of forty-eight hours, shewing the advantage of having a large supply of sulphuric acid.*

"Experiments with Smee's Battery of Platinized Silver.-The acid solution was of the same strength as before, and the sizes of the zincs and platinized silver the same as of the zines and platina formerly employed. The zincs were bent round the platina.†

"The porous vessels were of pipeclay. The same experiments repeated with unglazed porcelain, gave 10 cubic inches in two minutes; with very porous pipeclay, they gave as much as 15 cubic inches in two minutes, shewing the importance of attending to the nature of the porous vessel employed."

The most advantageous method of arranging a Smee's battery is packing the zincs and platinized silvers in the manner recommended by Dr.

Time, 2 minutes..

After 5 minutes.

Cubic inches.

3.

2.6

"Second Experiment.-The zincs being raised out of the acid, cut in two, and re-immersed.

Time, 2 minutes

After 5 minutes

Cubic inches.

1.6

1.6

"Third Experiment.-The zincs and platinized silver being removed, the acid remaining untouched; the platinized silver plates were bent round the zincs.

"Fourth Experiment. The platinized silver cut in two.

"Supposing, from these experiments, the same quantity of electricity to be developed, whichever of the opposed surfaces of the two metals be the greater, I placed in separate glasses five zinc cylinders, one-inch diameter, immerged eight-tenths of an inch in the acid; platina foil, connected by binding screws with the zincs, was rolled into cylinders two-tenths of an inch in diameter, and then immersed in pipeclay tubes one inch deep.

Cubic inches.

Time, 2 minutes

.....

After 10 minutes..

1.0

1.0

"Second Experiment.—Platina foil of the same size as the zincs, and zinc rods of the same diameter as the platina cylinders, being employed, the effects were precisely the same.

Time, 2 minutes

After 10 minutes.

Cubic inches.

1.0

1.0

"Third Experiment-The zinc cylinders being made twice the diameter of the former, the quantity of gas generated in two minutes was the same as before, the increased number of lines of electrical force compensating the increased resistance offered by the acid solution.

"Fourth Experiment.-With cylinders twice the diameter of these, a very feeble current passed, the obstacle being too great to be overcome; by increasing the diameter of the porous vessels, and thereby of the nitric acid solution, which is a good conductor, the impediment is diminished, as shewn in experiment fifth. Thus Mr. Faraday in his tenth series, (also by Mr. Young, Phil. Mag., s. 3, vol. x., p. 241) placing the package on supports so as to allow the sulphate of zinc to fall to the bottom of the vessel, while the fresh acid rises to the surface."

Binks (Phil. Mag., s. 3, vol. xi. p. 68) finds, that in dilute sulphuric acid, the size of the copper compared to a given surface of zinc, to produce a maximum effect, should be 16, that of the zinc to a given surface of copper being 7; while in a galvanic arrangement, in which the zinc is immersed in dilute sulphuric acid enclosed in a membranous bag, and the copper in a surrounding solution of sulphate of copper, the proportion of zinc to copper was as one to eight, the impediment to the passage of the current being double in the latter case what it was in the former.*

Fifth Experiment.-Five cylinders of zinc, 10 inches high, diameter, were placed in glass vessels containing sulphuric acid, as before. Into these were placed cylindrical earthenware vessels, 1 inch diameter, containing pure nitric acid; slips of platina foil were rolled into cylinders as before.

"From these data may be calculated the heights of the zinc pipes, and the weight of platina foil required to obtain any given decomposition to be employed, as shewn by Jacobi, either as a motive power, or applied to light-houses, to the polariscope, or to the fusion of refractory substances. For the latter purposes I had fixed to a strong shallow woolf-bottle, two tubes with glass cocks, and to them tubes containing chloride of calcium, applied to a Daniell's jet, playing upon a cylinder of lime rotated by clockwork. A third tube was inserted in the bottle, intended as a regulation of the pressure, or a safety-valve, in case of explosion."

Dr. APJOHN then made a brief verbal communication on the subject of the composition of Pyrope. This mineral, long confounded with garnet, is known to be distinguished from it by containing chrome, and by exhibiting, not the dodecahedral, but the hexahedral form. The best analysis of it, however, which are by Kobel and Wachtmiester, are obviously imperfect, of which no better proof can be given than that Gustavus Rose, in his Crystallography, does not attempt to give the formula of the mineral, but contents himself with enumerating the different oxydes of which it is composed. Under these circumstances, Dr. Apjohn conceived that a re-examination of the constitution of pyrope would not be without interest. He there

• "The experiments of Prof. Daniell have proved, that in the constant battery, when the generating surface formed the circumference of the arrangement, the force was only the half of that evolved when it formed the centre."-Phil. Trans., vol. cxxviii., p. 41.

"The dilute acid in the voltameter began to boil; the cause of the increase of decomposition, compared to what took place in the small cylinder, was the small stratum of sulphuric acid between the porous vessel and the zinc. For a continuous action, the zinc pipes, sealed at one end and amalgamated, should be connected, by pipes at top and bottom, with an earthenware vessel containing the sulphuric acid."

fore undertook its analysis; and the result has been that he has detected in it yttria, one of the rarest of the earths; one, in fact, which had previously been known to exist only in a few minerals of exceeding scarcity. The yttria was insulated in the following

manner:

The mineral being fused with carbonate of potash, and the silex separated in the usual way, the peroxyde of iron, alumina, and yttria were precipitated together by a mixed solution of ammonia and salammoniac. The alumina was taken up by caustic potash; and to the iron and yttria, dissolved in a minimum of muriatic acid, such a quantity of tartaric acid was added, that upon subsequently pouring in ammonia in excess there was no precipitate produced. The iron was now removed by sulphuretted hydrogen; and the solution evaporated to dryness, and ignited in a large platinum crucible, so as to volatilize the ammoniacal salts and burn away the carbon of the tartaric acid, left the yttria slightly coloured by oxyde of chrome. From this latter substance it is separated, but not perfectly, by the action of a dilute acid; and by the addition of ammonia, or caustic potash, to the solution, the yttria is again recovered. That the substance thus obtained is yttria, seems proved by the following considerations :

It is separated, though not completely, from acids, by ammonia largely diluted with sal-ammoniac, and hence cannot be one of the alkaline earths.

It is insoluble in potash, and is, therefore, not alumina or glucina. After ignition it dissolves readily in dilute acids, and is hence not zirconia or thorina. From zirconia it is further distinguished by its saline solutions being precipitated by ferrocyanide of potassium.

It is not oxyde of cerium, for it does not redden in the exterior flame of the blow-pipe, and because its salts are not precipitated by the sulphate of potash. The quantity of the yttria amounts to at least 3 per cent.

Dr. Apjohn is still engaged in investigating the composition of pyrope; and expressed his intention of bringing his results on a future occasion in a more detailed form under the notice of the Academy, when he hoped also to be able to assign the true formula of the mineral.

Mr. CLIBBORN made the following communication on the subject of the Leyden Jar::

"In Brande's Manual of Chemistry, vol. i., 3rd edition, p. 76, I find it stated, that if one Leyden jar be insulated, with its internal surface connected with the positive conductor, another jar may be charged from its exterior coating; and if this second jar be insulated, a third may be charged from its exterior coating, and so on for any number of jars, provided always that the exterior coating of the last jar be connected with the ground.'

"As my electrifying machine was but small, it occurred to me that I might economise both time and labour by constructing a bat