قراءة كتاب The Introduction of Self-Registering Meteorological Instruments
تنويه: تعرض هنا نبذة من اول ١٠ صفحات فقط من الكتاب الالكتروني، لقراءة الكتاب كاملا اضغط على الزر “اشتر الآن"
The Introduction of Self-Registering Meteorological Instruments
geared to the hour pinion. A discussion of the clock's "reduction to practice" began the involvement of Robert Hooke, who was "instructed" in September 1664 to make "a pendulum clock applicable to the observing of the changes in the weather."[8] This tribute to Hooke's reputation—and to the versatility of the mechanic arts at this time—was slightly overoptimistic, as 15 years ensued before the clock made its appearance.
Figure 2.—A contemporary drawing of Wren's "weather clock." (Photo courtesy Royal Society of London.)
References to this clock are frequent in the records of the Royal Society—being mainly periodic injunctions to Hooke to get on with the work—until its completion in May 1679. The description which Hooke was asked to supply was subsequently found among his papers and printed by William Derham as follows:[9]
The weather-clock consists of two parts; first, that which measures the time, which is a strong and large pendulum-clock, which moves a week, with once winding up, and is sufficient to turn a cylinder (upon which the paper is rolled) twice round in a day, and also to lift a hammer for striking the punches, once every quarter of an hour.
Secondly, of several instruments for measuring the degrees of alteration, in the several things, to be observed. The first is, the barometer, which moves the first punch, an inch and half, serving to shew the difference between the greatest and the least pressure of the air. The second is, the thermometer, which moves the punch that shews the differences between the greatest heat in summer, and the least in winter. The third is, the hygroscope, moving the punch, which shews the difference between the moistest and driest airs. The fourth is, the rain-bucket, serving to shew the quantity of rain that falls; this hath two parts or punches; the first, to shew what part of the bucket is fill'd, when there falls not enough to make it empty itself; the second, to shew how many full buckets have been emptied. The fifth is the wind vane; this hath also two parts; the first to shew the strength of the wind, which is observed by the number of revolutions in the vane-mill, and marked by three punches; the first marks every 10,000 revolutions, the second every 1,000, and the third every 100: The second, to shew the quarters of the wind, this hath four punches; the first with one point, marking the North quarters, viz. N.: N. by E.: N. by W.: NNE.: NNW.: NE. by N. and N.W. by N.: NE. and N.W. The second hath two points, marking the East and its quarters. The third hath three points, marking the South and its quarters. The fourth hath four points, marking the West and its quarters. Some of these punches give one mark, every 100 revolutions of the vane-mill.
The stations or places of the first four punches are marked on a scrowl of paper, by the clock-hammer, falling every quarter of an hour. The punches, belonging to the fifth, are marked on the said scrowl, by the revolutions of the vane, which are accounted by a small numerator, standing at the top of the clock-case, which is moved by the vane-mill.
What, exactly, were the instruments applied by Hooke to his weather clock? It is not always easy even to guess, because it appears that Wren was actually the first to contrive such a device and seems to have developed nearly as many instruments as Hooke. It might be supposed that Hooke would have adapted to the weather clock his wheel-barometer, introduced in 1667, but it also appears that Wren had described (and perhaps built) a balance barometer before 1667.[10] As to the thermometer, we have no evidence of original work by Hooke, but we do have a description of Wren's self-registering thermometer, a circular, mercury-filled tube in which changes in temperature move "the whole instrument, like a wheel on its axis."[11]
The hygroscope (hygrometer) probably existed in more versions than any other instrument, although we know nothing of any versions by Wren. Hooke may have used his own "oat-beard" instrument.[12] Derham follows his description of the clock—which has been quoted above—with a detailed description of a tipping-bucket rain gauge invented by Hooke and used with the clock. He also notes that in 1670 Hooke had described two other types of rain gauge in which a bucket was counterbalanced in one case by a string of bullets and in another by an immersed weight. But here again, Sprat records the invention of a tipping-bucket gauge by Wren before 1667.
Hooke has been generally regarded as the first inventor of an anemometer, in 1662.[13] But this invention was a pressure-plate gauge—that is, a metal plate held with its face against the wind—whereas the gauge used with the weather clock is clearly a windmill type, of which type this may be the first. Wren also had an anemometer, but we have no description of it. Hooke's account does not refer to other instruments which the weather clock is supposed to have had, according to a description quoted by Gunther, which concludes the enumeration of the elements recorded with "sunshine, etc."[14] One can only wish for further information on the mechanism by which the punches—or in Wren's clock, the pencils—were moved. But it is apparent that Hooke's clock was actually used for some time.
Figure 3.—Dolland's "atmospheric recorder": 1, siphon and float barometer; 2, balance (?) thermometer; 3, hygrometer; 4, electrometer; 5, float rain gauge; 6, float evaporimeter; 7, suspended-weight wind force indicator; 8, wind direction indicator; 9, clock; 10, receivers for rain gauge and evaporimeter. (From Official ... Catalogue of the Great Exhibition, 1851, London, 1851, pt. 2).