VOL. XLIX.] PHILOSOPHICAL TRANSACTIONS. 645 



Fig. 10, (ab) the milk-boiler, with the broad rim (cd), and perpendicular rim 

 (cedf) soldered to the horizontal rim ; the perpendicular rim to enter the circular 

 groove (ef) 4 inches deep full of sand, to prevent the ascent of the smoke from 

 the fire-stove. 



LFII. On the Return of the Comet, expected in 1757, or 1758. By T. Barker,* 

 Esq. Dated Lyndon, near Uppingham, Rutland, Dec. 17, 1754. p. 347, 



As we expect the comet of 1531, 1607, and l682, to return in 1757 or 1758, 

 it is proper to be aware where to look for it. But that will be very different, 

 according to the time of the year it comes ; and its period is not sufficiently 

 known to fix the month of its next perihelion, which should be July 25, 1757, 

 according to its last period ; but the length of that before would make it Oct. 

 25, 1758. Mr. B. has therefore, in 12 short tables, given the apparent path 

 of the comet, supposing its perihelion any month in the year, with its curtate 

 distance from the earth ; and the first 2 articles of each are the places which it 

 would probably begin to appear in. These will show in general the course of the 

 comet, especially at its first appearance, which is most wanted ; but cannot be 

 depended on where its motion is swift, and may be 40° in a day, the beginning 

 of May, or middle of October. From these tables, compared with the scheme, he 

 made another, where the comet would begin to be seen any month in the year. 



To construct the places, on a large sheet of pasteboard, he divided the cir- 

 cumference of a circle, of 10 inches radius, into degrees, for the magnus orbis. 

 On the right point of the ecliptic and focal length he drew a parabola like that 

 observed in 1 682, round the sun, the centre of the circle, and marked every 4th 

 day's motion from the perihelion, and the line of its nodes. The co-sine of the 

 comet's inclination set off on perpendiculars to this, towards the several points of 

 the parabola, forms the projection of it, or points in the plane of the ecliptic over 

 which the comet is at any time perpendicular. 



To find the comet's place at any time, count how long it is before or after its 

 perihelion, and mark the place in the projection of the parabola : lay one edge 

 of a parallel-ruler through that point, and the place the earth is then in, and the 

 other edge passing through the sun, will cut the magnus orbis at the geocentric 

 longitude of the comet : the tangent of the comet's inclination making the per- 

 pendicular from the comet's projected place to the line of nodes, the radius is the 

 tangent of its apparent latitude, making the curtate distance of the comet from 



• Mr. Barker died at Lyndon, in May 1803, at an advanced age. He was of an ancient and re- 

 ipectable family in Rutland. His father was a celebrated Hebrew scholar, and his mother wa» 

 daughter of the pious and learned Wm. Whiston, in whose Memoirs may be seen frequent notices of 

 the family. Besides Mr. B.'s regular Annual Registers of the Weather since the year 1771 j and se- 

 veral other papers, in the Phil. Trans., he was author ot some other separate publications, both on 

 astronomy and theology. 



