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 ther- 

 mometer, 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 fiU'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 

 ihe 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 1 00 revolutions of the vane- 

 Qiill. 



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-barome- 

 ter, introduced in 1667, but it also appears that 

 Wren had described (and perhaps built) a balance 

 barometer before 1667. 1° As to the thermometer, 

 we have no evidence of original work by Hooke, 

 but we do have a description of Wren's self-register- 

 ing thermometer, a circular, mercury-filled tube in 



"> Wren's clock and its wind vane and anemometer, ther- 

 mometer, barometer, and rain gauge are described by T. Sprat, 

 The History oj the Royal Society . . . , London, 1667, pp. 312-313. 

 On the balance-barometer, see also footnote 28, below, and 

 figure 4. 



which changes in temperature move "the whole in- 

 strument, like a wheel on its axis." ^' 



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. '- 

 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 iinmersed 

 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.'^ 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 enumera- 

 tion of the elements recorded with "sunshine, etc." '* 



n Since the above was written, additional information on 

 this clock has been published by H. E. Hoff and L. A. Geddes, 

 "Graphic Recording before Carl Ludwig: An Historical 

 Summary," Archives Internationales d'Histoire des Sciences, 1959, 

 vol. 12, pp. 1-25. Hoff and Geddes call attention to a report 

 on the clock by Monconys, who saw the instrument in 1663 

 and published a brief description and crude sketch (Balthasar 

 Monconys, Les Voyages de Balthasar de Monconys; Documents pour 

 rHistoire de la Science, avec line Introduction par M. Charles Henry, 

 Paris, 1887). Monconys says that the thermometer "causes a 

 tablet to rise and fall while a pencil bears against it." The 

 instrument shown in his sketch resembles a Galilean thermo- 

 scope. 



12 Hooke's "oat-beard hygrometer" was described in 1667, 

 but Torricelli seems to have invented the same thing in 1646, 

 according to E. Gerland, "Historical Sketch of Instrumental 

 Meteorology," in "Report of the International Meteorological 

 Congress Held at Chicago, 111,, August 21-24, 1893," O. L. 

 Fassig, ed., U.S. Weather Bureau Bulletin No. ?/, pt. 3, 1896, pp. 

 687-699. 



13 But a Dutch patent was awarded to one William Douglas in 

 1627 for the determination of wind pressure (G. Doorman, 

 Patents for Inventions in the Netherlands during the 16th, Vth and 18th 

 Centuries, The Hague, 1942, p. 127), and Leonardo da Vinci left 

 a sketch of both a wind pressure meter and a hygrometer {Codex 

 Atlanticus, 249 va and 8 vb). 



" Gunther, op. cit. (footnote 8), pp. 433, 502. 



PAPER 23: THE INTRODUCTION OF SELF-REGISTERING METEOROLOGICAL INSTRUMENTS 



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