HOROLOGY. 



141 



t beauty, and fanciful execution, but also for their utility. 



ng The French artists unwillingly admit our claim to this 

 invention ; and could they have brought forward docu- 



" ments to the contrary, it wuulij most readily have been 

 done. They maintain, that it coulU not have been in- 

 vented and improved at the same time by any <>ne man, 

 an opinion in which we must agree with them. A 

 wheel-cutting engine, and one which could divide al- 

 most any number, by means of an endless screw and 

 toothed wheel, was nude about 70 years ago by Hind- 

 ley of York, which came afterward* into the possession 

 of Mr Smeaton, from whom Mr hi ><1 purchased it SO 

 years ago. As Hindley knew what had been done in this 

 way by Dr Hooke, this seems to have been made in imi- 

 tation of his, with some additions and improvements, as it 

 is evidently not copied from that which is described in 

 Thiout's work, vol. i. p. 53, plate xxiii. fig. 1. siyd to 

 have been invented by M. P. Fardoil, watchmaker at 

 Paris. Ramsden's dividing engine, for which he got 

 considerable premium from the Board of Longitude, 

 was executed on this principle, the great merit of which 

 consisted in having a more perfect screw than had 

 hitherto been made. See our article GRADUATION, 

 vol. copious history of Dividing Engine*, 



and a full account of the engines invented by fiamsden 

 ad Troughton. 



( HAP. VII. 



CfeU 



THI first equation dock, which i* a very ingenious 

 contrivance to shew both mean and apparent time, was 

 made in London about 120 year* ago. The following 

 history of the invention is given by Berthoud in hi* 

 lint 



he meat ancient equation clock," *sy he, " which 

 ha* come to our knowledge, is that which was placed 

 in the cabinet of Charles II. King of Spain, and which 

 M mentioned at the end of The Artificial Rmle of Tim*, 

 by Sully, (edition 1717.) who give* the following ac- 

 count of it, from an extract of a letter of the Rv. 

 Father Kreaa, of the society of Jeans, written to Mr 

 union, watchmaker of the cahitirt of hi* Impe- 

 rial Mateaty, of the 9th January I7l5. 



" What Mr Baron Lcibmu says, in his remarks at 

 the end of Sully'* book; that if a watch or clock did 



of itself make the reduction of eoW lime to apparent, 

 it would be a very 6ne and convenient thing; a thi* 

 shjtct I have to tail you. that from the years 1 699 and 

 there has bean in the 



al end*d*un. (i 



and not with 

 : requiring to be 



> Majeaty, and in hi* 



plained the iiutntctoon*, which 



<*itli 



ke year* Ifiyyand 



rat.mrt ot 'King ( Marl, , II. 



;i dock with a roy- 

 ) made to go with 

 four hundred days 

 >. I have, by 



(Mngaj 



had order* to go every day to the palace during i 

 manth* to obserwe the said dock, and compara 

 the M n dial. And at that time I remarked, 

 hawed the equation of time ravaZ and 

 ly according to the Table* af ' 



it ith 

 that it 

 exact* 



:!, which are 

 farad bkewiae in the Bndalphina Table,.' Ac. 



Sully, at the end af the letter of which an extract baa 

 just bean given, nukes the following remarks, page !>: 

 hat the Rev. Father K resa relates of the dock of 



the late King of Spam, i= v c ry trur. It is more than 

 twenty years since such clocks were made in London, 

 anil I believe that I am the first who applied this me- 

 chanism (for equation) to a pocket watch, twelve or 

 fourteen years ago." 



The following is a description of a very excellent and 

 curious equation clock, which belonged to the late Ge- 

 neral Clerk. It was left, with several other things, to 

 the late Sir John Clerk, and entailed on the house of 

 Pennycuik. 



The clock goes a month, strikes the hour, and has a Inscription 

 strike silent piece. The 'scapvment of it is made after . f " r|Y*"' 

 that of John Harrison's, requiring no oil to the pallets; IK 

 (see p.l 19 )andthe pendulum is a gridiron compensation 

 one, composed of five rods, three of which are steel, the 

 other two of zinc, or some compound of zinc. On the 

 dial are seen the hours, minutes, and seconds, and their 

 hands. The minute hand keeps mean or equal time ; 

 the equation of time is given by a hand with a figure 

 of the sun on it, which makes a revolution every 

 hour as the minute hand does, only for the most part it 

 goes sometimes a very little slower, and sometimes a 

 little faster than the minute hand, keeping solar or un- 

 equal time, and shows at all times when the sun is 

 on the meridian. The age and phases of the moon are 

 also represented, the days of the year and of the month, 

 the degrees of the ediptic, and the signs of the zodiac, 

 the rising and* setting of the sun, the length of the day, 

 &C. The dial is a twelve inch arched one. Concentric 

 with the arch, is a sort of ring plate wheel of 365 tccili, 

 making its revolution in a year, or 365 <lavs. ludiame- 

 ibout 8 inches, and the breadth of the rim or ring 

 1 4 inch nearly. On this ring plate, at the outermost 

 circles containing divisions, are laid down tlir days of 

 the year ; and on the space next within, are the names 

 of the months, the days being numl>ered by the figures 

 10, 80, .SO, and so on. The next circles contain the 

 360 degrees of the ecliptic ; the space within h.. 

 signs of the zodiac, and the numbers 10, 1:0, and > 

 "wVf ' for the degrees in every sign, an-! i < 1.1 -pond- 

 ing with tne days of the year and of the month when 

 the sun is in any of these signs. The innermost circl. 

 contain what may be called the division* of the semi- 

 diurnal arc*. On the space outside of this, are marked 

 the corresponding hour figures in Roman character*. 

 This i* what give* the time of the rising and sotting of 

 the aun, and tne length of the day. 



In the annual plate ring, arcrivctted six small bras* 

 pillars, on* inch and one tenth of an inch in height, 

 whose imraaite end* are screwed by kteel screw*, and 

 their heads sunk into a plain ring wheel neatly crossed in- 

 to six arms, the diameter being five inches and three quar- 

 tan of an inch, and the breadth of the rim three-eighth* 

 of an indi. The back of thii^ain ring is distant from 

 the back of the annual plate ring one inch and a 

 quarter. The plain ring u at the centre, screwed on 

 a bra** socket, having a square hole in it Within 

 the frame of the clock movement, and at a perpendicu- 

 lar distance of six inches from the centre win el !. 

 a steel arbor is run in, and at one end prolonged ul>oiit 

 an inch and a half beyond the fore frame plate, some- 

 what like a tud. Tlir pivot in the lore plate is of. 

 such a length and thickness, a* to allow a *quare mi 

 its outside. It is on this square that the equation 

 elliptic plate i* put, and above it i put on the annual 

 plane ring hy means of its socket, with a tqunre hole in 

 it. That part of the arbor which i" above this socket 

 i* round, and serves a* a stud for the moon'* age ring. 



Table* wen calculated bj out fin* Asuooaaui Roysl Mi rlamtssd, at Crctnwfctu 



