26 REPORT — 1 853. 



the motion of the surface-water ; by the movements of the boat, (2) the relative 

 motions of the surface-water, and that at the depth of the current-measurer, at the 

 first trial ; an indication of the changes at other depths ; and, on reeling in the wire, 

 the highest and lowest temperature would be shown at each of the depths examined 

 (that is, when the changes were in one way, as from warm to cold), and thus the 

 several results might be compared with the SKr/ace-temperature taken at the com- 

 mencement, and at each change of depth. 



The cases in which such experiments would be the most interesting, would pro- 

 bably be found in places of the ocean where great differences of temperature are met 

 with at comparatively moderate differences of depth. In some of the positions 

 examined, for instance, by the officers of the United States Coast Survey, the tem- 

 perature was found to sink, from about 80° at the surface, sometimes to 70°, or even 

 65°, in depths not exceeding 120 fathoms, and down to 64° or 63° (near 20"^ lower 

 than at the surface), in depths of 120 ranging to 480 fathoms; whilst a tempera- 

 ture as low as 44°, or less, was met witli at the depth of about 700 fathoms. Now, 

 in such cases — cases pievailing extensively within and about the edges of the Gulf- 

 stream, or within the changes of surface-temperature in the transatlantic passage — 

 we should probably obtain by the processes described results of no ordinary interest 

 and importance. 



The results, it must be admitted, could only be proximate ; for the boat, moved 

 by the deeply-sunk current- measurer, it is obvious could not follow vertically above 

 it ; but under the action of an obliquely ranging wire, when both boat and wire must 

 present a force of resistance, the boat must take a position behind. Yet, if the cur- 

 rent diflFerences were considerable in velocity and direction, perhaps experiments 

 continued for a few hours at a time, and repeated under a due variety of circum- 

 stances, might afford data for mathematical determinations of resistance and cor- 

 rections. And, in certain cases, in regions where the great oceanic currents overlay 

 one another, like those from the Polar Seas and the Tropics, conclusions abundantly 

 satisfactory might, no doubt, be realized. 



Meteorology. 



On a proposed Barometric Pendulum, for the Registration of the Mean 



Atmospheric Pressure during long Periods of Time. By W. J. Macquorn 



Rankine, C.E., F.R.S.S. Loud, and Edinb. 



The author proposes to use the variations of the rate of a clock to determine the 

 mean barometric pressure during long periods. 



For this purpose the clock should be regulated by a centrifugal or revolving pen- 

 dulum, part of which should consist of a siphon barometer. The rising and falling 

 of the mercury would affect the rate of the clock ; so that from the number of revo- 

 lutions of the pendulum in a given time might be deduced approximately the mean 

 height of the mercurial column during that period. 



The author investigates the formulae to be used for this purpose, and points out 

 the nature and mode of determination of the corrections required for temperature, 

 obliquity of the barometer, and centrifugal force, and also for the difference between 

 the square root of the mean of the squares of the barometric heights, which is the 

 quantity ascertained in the first instance, and the mean of the heights, which is the 

 quantity sought. 



On a Concentric Iris, as seen from the ridge of Snoivdon, near the summit, 

 on the morni»g of the \$th. of June 18.53, about an hour after sunrise, pro' 

 jected upon the clouds floating along the sides of the 3Iountain. By 

 William Gray, Jun 



The iris continued in sight about an hour, becoming gradually depressed into the 

 shadow thrown by the mountain on the clouds. 



When first seen the colours were exceedingly brilliant, and exhibited four concen- 



