KNDWLl-.DC.l-.. 



Jui.v. 1912. 



tlii'Si- nunfiiiiiits |>l:i\s in the design, it will !«• wi'il 

 to aiiiilvsi' till- movements wliich have resulted 

 in l-'ij^iire 276. 



In this case tlie tracinj^ |H)int (t ) of the pantograpli 

 described a circle. This tnotinii was obtained l)y 

 removing; one of the runners and clamping the 

 remaining one round which tlie radial arm (B) 

 rotated, carrying with it the tracing ])oint. The 

 position of the tracing point along the arm governed 

 the diameter of the circle. 



Between the upper and losver spur w IkiIs i)eneath 

 the elliptic table gears were introduced so that 

 twent\-four circles were drawn to each complete 

 rotation of the ellipse table. Gears were also 

 introduced between this and the central sliding table 

 so that the elliptic table revolved eight times while 

 the central sliding table (E) moved once forward and 

 backward. This, together with the fact that the 

 runner was clamped a little eccentric on the elliptic 

 table, is responsible for the eight nodes in each of 

 the six arms, while there are twenty-four complete 

 circles between any node and the next. 



Only the lower of the two central sliding tables 

 was used, and the distance it traversed was 

 responsible for the length of the arms in the design. 



The drawing table revolved centrally, one com- 

 plete revolution coinciding with six double 

 movements of the central sliding tabic. Thus the 

 design has six arms. 



For line work, glass pens arc u.sed. .\ |»ie( e of glass 

 tubing is drawn to a point and ground down until 

 when the point is immersed in water and the other 

 end blown down, a few bubbles are seen to slowly 

 escape. The pen is filled with a solution of aniline 

 dye. 



The diagrams illustrating this article have, of 

 necessity, to be coarse and give little idea of the 

 delicacy that can be attained. 



Very beautiful effects are produced by drawing 

 such a design as Figure 275 in blue, turning 

 the drawing table through 36' and repeating the 

 same design in crimson. The form of the ellipse 

 may also be slightly altered and the new design 

 superimposed on the previous one, as was done in 

 Figure 279. 



,\n original and very convenient method for 

 holding the gear wheels in position is used on this 

 machine, and an examination of Figure 271 will 

 perhaps make the method clear. The required 

 wheels are slipped on to a drum and clamped 

 together by a milled nut. The drum and wheels are 

 then slipped together on to a spindle round which 

 they can freeh' revolve. The spindle is clamped to 

 the baseboard of the machine by means of another 

 milled head, which springs a forked piece of 

 lancewood, causing it to press the base of the spindle 

 firmlv down to the woodwork of the machine. They 

 can thus be clamped in any position. 



SOLAR DLSTLRBAXCES DURING MAY, 1912. 

 By FRANK C. DENNETT. 



During May the Sun's disc appeared free from disturbance 

 on thirteen days— 7th. 12th. 15th ti) 24th. and 30th. and on 

 six others^Sth, 9th to 11th, 25th and 26th, — only faculae 

 were visible. The central meridian at noon on May 1st 

 was 2° 1'. 



The great faculic disturbance which originally appeared 

 around the spot disturbance No. 1 in longitude 295° has 

 continued visible, extending forward in longitude, and now 

 reaching to 330°, but scarcely extends so far back as its 

 place of origin. It is to be noted that the groups of spots 

 Nos. 1. 3, 4 and 6 have all appeared within this area. Only 

 one other faculic disturbance was recorded during the month, 

 a small one near longitude 68° and in somewhat high South 

 latitude, but its exact position was not measured. 



No. 4 is an outbreak belonging to the April list, but shown 

 on the present chart as it continued visible until May 6th. 



No. 5. — A black pore visible on the 13th and 14th only 

 appearing smaller on the later date. On the afternoon of the 

 13th it was followed by a smaller grayish pore. 



No. 6. — A group of very small pores, constantly changing 



in appearance, at the western end of the great faculic 

 disturbance. Although never at one time more than 

 52,000 miles in length it seems to have been in reaUty 

 89.000 miles in extent, and was seen from the 27th until 

 the 29th. 



No. 7. — A group of three spotlets and a pore seen on the 

 31st, increasing during the day, the eastern and western spots 

 each having about three umbrae. The length of the group 

 increased to over 60,000 miles, and the diameter of the lower, 

 eastern, spot was 11,000 miles. It was only seen until June 

 the 2nd, after which it passed round the limb. With 

 the spectroscope it was finely seen, a considerable dark 

 hydrogen flocculus just west of one of the spots branching 

 off the C line on the red side, whilst the D.s line of helium 

 was dark and thick on the 31st. 



The chart is constructed from the combined observations of 

 Messrs. J. McHarg, A. A. Buss, E. E. Peacock, and the writer, 

 made in places so far separated as Lisburn, Manchester, 

 Bath and Hackney. 



DAY OF MAY, 1912. 



