Fig. 1 is a vertical or ground plan of the wheel-work. Fig. 2 shows it in section as applied to the watch. Description:-The fuzee wheel is assumed to turn once round in 4 hours; to the back of the fuzee wheel is made fast by pins a small wheel of 20 teeth, which drives a wheel of 40 teeth once round in 8 hours. The axis of this wheel of 40 teeth ascends through the frame DD of the watch (shown in Fig. 2 at c); on this axis is made fast a small wheel of 19 teeth, which takes into and drives round a wheel of 57 teeth, shown in Figs. 1 and 2 at A; now as the small wheel 19 turns once round in 8 hours, it is evident that if 19 be made to turn a wheel of 57 teeth, that wheel will turn once round in 24 hours; accordingly, the small wheel 19 drives wheel A (in Figs. 1 and 2), of 57 teeth, causing it to turn round in 24 hours precisely, which wheel is made to carry an index, having on its extremity a small ball representing the Sun; the small wheel 19, also turns a wheel under wheel 57, having 59 teeth; consequently, this wheel of 59 must move much slower than wheel 57, (in the ratio of §, so much so, that instead of turning round in 24 hours, with wheel 57, it will not turn round in less time than 24 hours 50 minutes 31 seconds 35 thirds; the hollow axis of wheel 59 ascends through the hollow axis of wheel 57, and carries an index, carrying on its extreme point a ball representing the Moon, as shown in Fig. 2. Thus, by this simple contrivance, the Sun will make a revolution round the 24 hours on the dialplate of the watch in 24 hours, and the Moon in 24 hours 50 minutes 31 seconds 35 thirds. Figs. 1 and 2, in the above cut will be easily understood, as both figures and letters on them have reference to the same details. 268 In concluding his description of this Clock and Watch in his MS. "Common Place Book," he says, 268 If 57: 24 h. : : 59?----59 × 24 = 1416÷57 = 24 h. 50 m. 31 s. 35 thds., which is a motion too slow by 3 s. 13 thds. The true mean apparent diurnal revolution of the Moon is accomplished in 24 h. 50 m. 28 s. 22 thds. 48 fourths. (See note 154). We may here mention that the late Mr. Andrew Reid, watchmaker, London, who died at Brixton in 1835, aged 85, had often told us that he was on familiar terms with Ferguson; was often at his house in Bolt Court, Fleet Street, and had there seen several works of watches fitted up with a variety of astronomical mo tions, as also strong works noted for their correct time-keeping-one pair of double silver cases suited all the works. These cases, with one of the works, came into Mr. A. Reid's possession in 1801, from whom it was purchased by the writer. "I contrived this Clock in July, 1770, and put the movement of an old Watch to it, by means of which it is now going very well (March 10th, 1775); the two wheels A and B are only of Card-paper, and yet I have reason to believe that they will last 30 years.-J. F.” No traces whatever of either this Clock or Watch are now to be found. A writer in the "Operative Mechanic" "thinks it extremely probable" that Ferguson "had the dial of the Clock at Hampton Court in his eye when he contrived this Clock." See the "Operative Mechanic, and British Mechanist," p. 495. We are of a different opinion; although the Clock at Hampton Court shows the apparent daily revolutions of the Sun and Moon, -it does not exhibit the rise and fall of the tides; besides, Ferguson made a Clock in 1747 which exhibited the apparent motions of the Sun and Moon. (See pp. 113-120). TIDE ROTULA-Sometime during this year, Ferguson contrived and made a Tide Rotula, which consisted of one fixed or immoveable card of about 8 inches in diameter, having round its circumference twice twelve hours in Roman characters; above this immoveable outer card is a circular moveable card, having in a broad circular space round its circumference, the names of many Seaports in their relative positions to times of High water; within this circle of names of Seaports there are two other concentric circles,-the first having round it twice twelve hours in small Roman characters, the second, or interior circle, has round it the 29 days and other divisions of the Moon's age, and round the centre of this circle there is a black elliptical shade for producing the varied phases of the Moon through a small circular opening in the card above, and done in the same way as in the Clock last described. Above this lastmentioned card there is a smaller one having a Moon fixed to it, and directly under that is the small circular opening in which are exhibited the phases of the Moon as before noticed; round the centre is the figure of the Earth and some of its several circles, surrounded by an ellipsis representing water; all which particulars are shown in the annexed woodcut of the Rotula. Of this new Tide Rotula, the following is Ferguson's description, from which it will be seen that this instrument is only a modification or improvement of the Tidal Clock, for showing the times of High and Low water at London Bridge, just described. "This Rotula," says Ferguson, "is only an improvement on the Clock just described, by making it show the time of the Day and Night in the most remarkable places in the world at any instant of time at London, or at any other given place, without one single additional wheel. As it is in the scheme,-(without being made to go by means of a clock or watch, or any other method),-it is not useless; for, if you put London to the time of the day or night there, all the other places will point to the time of the day or night then opposite to them respectively. If you put the narrow black slip, under the Moon, to the day of the Moon's age (seen through the opening) on the middle plate, the same slip will cut the time of the Moon's coming to the meridian for that day, in the circle of 24 hours on that plate, and the other slip (directly opposite to the words, High Water) will cut the time of High water at London Bridge on that Day, in the same circle of 24 hours. And at any time, if London be put to that time, and the Moon's slip to the day of her age, you may then know the state of the Tide at London, by the position of the elliptical shade; the longest diameter of which will be even with the two XII's. in the outermost circle of 24 hours when it is High Water at London Bridge, and even with the two VI's when it is Low Water. In the intermediate times, the position of the elliptical shade shows whether the Tide is ebbing or flowing.-J. F., 1770." 269 "INTRODUCTION TO ELECTRICITY," PUBLISHED. In 1770, Ferguson went to press with a new work-very different from any of his previous Treatises-viz. an Elementary Treatise on Electricity, a small octavo of 140 pages, illustrated by three folding-plate engravings of the Electrical Machine and apparaThis work has passed through several editions,—viz. in 1770,—1775,—1778,-1790,-1823,-1825, &c. The following is copy of the title-page. (The edition of 1823 is in Brewster's Ferguson's Essays). tus. "An Introduction to Electricity-in Six Sections. I. Electricity Plate 1 exhibits the surface of a large table containing a variety of apparatus. On one end of it is fixed a Globe Electrical Machine, with multiplying motion-in front are three large Leyden Phials,-A Florence-flask,-A Thunder-houseand the Conductor is furnished with "A ring of bells,"-Pithballs, Star Wheel,-Attraction Plates,-Feathers, Spichar, &c., probably the same machine and apparatus which he bought from Mr. Nairne, Optician, &c., Cornhill. Plate 2. View of the works and Dial-face of an Electrical Clock.-An Electrical Wheel-work Orrery.-A Mill.-Toothach instrument, &c. Plate 3. View of an Electrical Triple-pump.270 269 A Rotula-in the autograph of Ferguson-similar to that described, is in the possession of William Topp, Esq., Ashgrove, near Elgin, who kindly sent us a copy of it. In 270 We have a beautifully-executed Indian-ink drawing, by Ferguson, entitled "An ELECTRICAL MACHINE, with a new ELECTROMETER. vented by Mr. John Lane in Aldersgate Street, London; " and in the lower right-hand corner of the drawing we find, “J. Ferguson, Delin.”—also a wheel cut out of card-it has 45 teeth most accurately cut into it,-likewise a trundle wheel of 15 cogs, with three cranks formed on its axis, which appears to have formed part of Ferguson's Electrical Apparatus—probably part of the model of a mill, or electrical pump models. As just observed, Section VI. of this work is devoted to "Medical Electricity." Ferguson, after describing several curious cases and experiments performed on the subject, says, "For my own part, being but a young electrician, I can have very In this medical section, several curious cases are related. The following refer to himself and his wife : "I was once, at Bristol, seized with a sore throat, so that I could not swallow anything. Mr. Adlam, of that city, who is a fine electrician, came and drew many electric sparks from my throat, and in about half an hour after, he did the same again. He staid with me about an hour longer, and before he went away, I could both eat and drink without pain; and had no return of that disorder. I have relieved several persons in such cases, but never in so short a time as Mr. Adlam cured me." (Electricity, p. 125). Referring to his wife's case, he says, "One time my wife happened to scald her wrist by boiling water. I set her upon the glass-footed stool directly, and took sparks from the wrist. In a short time I found the redness of the skin (occasioned by the scald) begin to disappear, and she felt immediate relief. A linen bandage was then put round her wrist, and in a few hours after, I repeated the operation, which entirely cured her, and there was not the least blister on the skin, nor any difference in its colour from what it had before the accident. If it had not been taken immediately, and before a blister had risen, perhaps electrifying would have been of little or no service." (Electricity, pp. 130, 131). This concise treatise has been long out of print, and is now seldom to be seen. LECTURE ON ELECTRICITY. In the Catalogue of his Ap In looking over one of our old Catalogues we observe several articles of Ferguson's Electrical Apparatus, which belonged to a Mr. Desormeaux, probably bought by him at Mr. Ferguson's public sale, in March, 1777. Mr. Desormeaux's property was sold by public auction by Messrs. Jordan and Maxwell at their Rooms, No. 331 Strand, on 12th March, 1806. In the Catalogue, is the following Lot :-"A Set of Ferguson's Electrical Apparatus, consisting of Sundry Models of Mills and Pump-work, with an electrical model of an Astronomica: Clock, Showing the nature of an Eclipse, and pointing out the Moon's age and the Tides this Lot sold for £1 17s.' |