October. 1911. 



KNOWLEDGE. 



395 



line by pieces of wood that fit into the slot, are a half- 

 plate camera mounted on a bo.x. and a carrier to hold 

 a 12-in. bv 10-in. sheet of glass. The carrier is open in 

 front to avoid an\- shadows on the background placed 

 below, and both carrier and camera are clamped in 

 position on the standard hv thumb screws. The 

 tense copper w ires greatly increase the rigidity of the 

 whole thing. The apparatus is used in an ordinary 

 room close to the window, or preferably in a hay 

 w indow. porch, or greenhouse, or even outside. The 

 plant to he photographed rests on the glass plate, 

 and about three or four inches below it, to avoid 

 shadow s, is placed a sheet of white or grey cardboard. 

 A verv dark or black background is in this situation 

 unsatisfactor}-, for the glass plate then becomes a 

 looking glass and a double image of the plant is 

 seen in the photograph. \\'here a black background 

 is required the plant rests directly on a sheet 

 of dull black paper which is supported on the glass 

 plate. For colour work an interesting background 

 is often made bv a sheet of white cardboard w ith 

 one or several la\"ers of "chiffon" of different tints 

 laid on it. Gi\en a dozen or more pieces of 

 ■' chiffon."" a thin silky material, dyed half a dozen 

 different colours, almost any tint can be built up. 

 If the background is some three or four inches away 

 it will be sufticientlv out of focus to prevent any 

 slight irregularities in the material appearing in the 

 photogra[ih. This point should be tested before 



exposure by a careful inspection after the lens has 

 been stopped down sufficiently. Of course, it is by 

 no means always necessary or desirable to lay the 

 plant down to photograph it. Often much more 

 natural results are obtainable if the plant is held 

 erect in a vase of water, being sure that the vase does 

 not appear, with the background sufficiently far away 

 from it to be thoroughly out of focus. Even in this 

 position a sheet of glass immediately behind is often 

 of value, for it limits the depth of focus of the picture 

 and gives support to flimsy plants. In photograph- 

 ing plants we must remember that we are dealing 

 with li\ing things which actually move, especiallv 

 when an\- change takes places in the equilibrium of 

 their water-vascular system. Hence it is unwise to 

 pick flowers on a hot summer day, put them in a vase 

 of water and immediately give them a prolonged 

 exposure. Rather should they be left in water for 

 at least two hours so that the cells of the plant may 

 accustom themselves to an abundant water supplv. 

 .\gain, when flowers are taken out of water and put into 

 position to be photographed it is just as well to cover 

 the cut stalk, if it does not appear in the photograph, 

 w ith a small piece of moistened cotton-wool to prevent 

 "fading fog."' \\'here the light is poor both in the studio, 

 and the field, focussing is greatly assisted by placing 

 a small scrap of printed paper close to and in the 

 same plane as the principal object to be photographed, 

 of course removing it before the exposure is made. 



SOLAR I)ISTURHANCP-:S DrRlXCx ATGL'-ST. 191 1 

 Bv FRANK C. DENNETT. 



DlRlNG August the disc appeared to be quite free from 

 disturbance on the 1st. 4th and 26th until 31st. whilst only 

 faculae were seen on the 2nd, 3rd and ISth until 25th. The 

 longitude of the central meridian at noon on .August 1st was 

 15° 29'. 



No. S2. — The most conspicuous outbreak of the month, first 

 seen within the limb on the 5th. The umbra of the large spot 

 was bridged on the 7th. and h.id an e.xtension eastwards, with 

 a small companion following. During the 8th and 9th other 

 spotlets formed, and changed, indicating considerable activity, 

 and the inner border of the penumbra of the large spot was 

 bright from the 7th until the 10th. Only a minute pore 

 remained as its solitary companion on the 11th, when the spot 

 had dwindled considerably. On the 13th, there were two 

 closely placed umbrae, and on the morning of the 14th, when 

 last seen, only one. The maximum diameter of the spot was 

 over ten thousand miles, and the length of the group over 

 forty thousand miles. 



No. 5i. — Two pores amid brilliant faculae had come round 



the limb on the 13th, the rear one being 2° farther north, and 

 a similar distance eastward of the leader. They died away 

 on the 15th. 



No. 34. — A pair of pores three degrees apart had broken 

 out on the 15th. next day the rear one had closed up. but the 

 area appeared disturbed, and on the 17th, when last seen, the 

 pore appeared cut in half by a bridge. 



No. 35. — A solitary pore only seen on the 16th. There 

 may be a very small error in its position. The dotted areas 

 upon the chart indicate the positions of faculic areas ; that 

 around No. 34 being observed on the 7th and Sth : that at 

 205° from the Sth until the 10th. The group around longitude 

 153° on the 13th. Not the least interesting facuUc distur"bance, 

 however, was a bright group on the 19th, in 60° south latitude 

 near longitude 67°, seen until the 23rd, though its brilliance had 

 decreased. The general granulation of the disc appeared 

 coarse over the south-eastern quadrant on the 27th. 



Our chart is constructed from combined observations of 

 Messrs. John McHarg. E. E. Peacock, and E. C. Dennett. 



20 33 "tO 50 63 70 8J M 101 110 i20 150 140 ISO 160 170 



190 XO aO 120 230 2W 250 260 270 



290 300 Jio m m no jso xo 



