First Report on the Hourly Observations of the Thermometer at the Plymouth Dockyard, Lat. 50° 21′ N., Long. 47° W. By Mr. W. S. HARRIS, F.R.S., &c. At the meeting of the British Association in September, 1831, the Sub-committee of Mathematical and Physical Science deemed it advisable to recommend, "that the Association should employ all the means in its power to procure a Register of the Thermometer during every hour of the day and night, to be kept at some military or naval station in the South of England," considering that the progress of meteorology materially depends on a thorough acquaintance with the phænomena of diurnal temperature. Soon after this judicious recommendation, two registers were commenced at Devonport near Plymouth; one under the superintendence of the late Mr. Harvey, F.R.S., &c., the other under my own. The former was undertaken at the immediate request of the Association. The latter was offered to its notice more as an individual contribution; it had been already contemplated, and was suggested by a series of meteorological inquiries carried on at Plymouth for several successive years. In speaking of Mr. Harvey, it is impossible to withhold the expression of that just tribute of respect due to the memory of an individual whose talents so greatly contributed to advance him in the estimation of the scientific world. The Association has lost in Mr. Harvey a zealous and able member, whose natural powers were carefully and most industriously cultivated. Had he lived, our Reports would have doubtless been greatly enriched by the results of his labours on this occasion. His register, from the decline of his health, is however, not continued for a sufficient time to render it available to the purpose for which it was undertaken. I have, through the kindness of Mrs. Harvey, been put in possession of all the observations received; these have been carefully discussed and compared t. So far as they go they are of consequence, although only noted for every two hours ‡, since they enable us to observe the influence of local circumstances on the indications of two similar thermometers placed within a short distance of each other. In order to obtain effectually such an hourly register as that *First Report, p. 49. + Mr. George Harvey has very kindly assisted in the discussion of these observations. Second Report, p. 574. in contemplation, an early application was made to Capt. Superintendent Ross, of the Dockyard, who interested himself in the undertaking, and with that kind liberality and courtesy for which he is so greatly distinguished, speedily afforded every just encouragement to the views of the British Association in this great endeavour to advance the interests of science. The hourly register, therefore, was soon commenced and carried on by the Warders and Officers of the Watch stationed at the gate, all persons of respectability and character*. It is due to them to say, that they have entered with more than common interest into the scheme, and have used every exertion to render the observations as perfect as possible. Little difficulty has hence arisen in obtaining the series of thermometric observations in the South of England, as contemplated by the Association, which for extent and accuracy may perhaps be considered the most perfect of any yet recorded. The thermometer is placed in an insulated position, just within a small circle of grass, about 60 feet above the level of the sea, and distant from it about 300 yards: it is sheltered from direct and indirect radiation, local heat, humidity, and other disturbing causes, by a light screen of latticed wood-work, quite open toward the north-east, and painted of a light colour; this screen is small, and is fixed on a single vertical pillar, as represented in Plate V. The lattices round the sides and beneath are made in the way of Venetian blinds, so that there is always a free current of air in circulation, and little chance of error from the absorption of heat by the screen. The latticed work below inclines at a sufficient angle to cut off all reflexion from the ground. There is a small sliding index of brass attached to the instrument, in the way of a T square; one arm projects over a slate, whilst the other can at any time be made to coincide with the surface of the mercury, and thus show with more precision its exact indications. A line may at the same time be drawn on the slate, coincident with the position of the mercury at the time of an observation; and thus when requisite we may again compare the entries made in the register during the night. The continued habit, however, of registering the observations has rendered this now unnecessary. The instrument itself is a valuable one; it was obtained from Mr. Cox, optician, of Devonport, whose skill in the construction of philo * Mr. Isaac Watts, also of the Dockyard, a gentleman of considerable attainments in science, educated at the late school of Naval Architecture at Portsmouth, has been so good as to interest himself in the success of this undertaking, and by an occasional attendance to the progress of the observations has done much in forwarding them. t Fith report of the Brit.Assoc. for the advancement of Science 1895 Tol.IV. PLATE 5.p.182. 0800 C. Goldsack del. JW Lowry foulp. |
