42 



♦ KNOWLEDGE 



[Jan. 16, 1885. 



but less closely in 2 than in 1, and still less closely set in 3. 

 Now if the page be set up where the light falls well upon 

 it, and then the observer retreat gradually from it, he will 

 find that at a certain distance 1 assumes the appearance of 

 a darkish grey square, while the separate spots in 2 and 3 

 remain still visible. Farther away 1 remains as a darkish 

 grey square, of just the same tint as before, but smaller ; 

 - appears as a light grey square, and the separate spots of 3 

 arc scarcely discernible. But passing farther away the 

 separate spots in 3 disajipear altogether from view without 

 having coalesced, as those of 1 and 2 successively did, so 

 as to form a tint. When last seen they are still at recog- 

 nisable distance from each other. Moreover the tints of 

 1 and 2 remain unchanged as you pass farther away. All 

 that happens with these squares is that they appear to 

 become smaller with increase of distance. 



These illustrative tests show that the mere visibility of 

 milky nebulosity in the star-depths tells something about 

 the diatribution and nature of the stars within the region 

 observed. Stars separated by considerable distances can 

 never appear like a diffused cloud. Stars of the same size, 

 but somewhat more closely set, will appear as a very faint 

 nebulosity if far enough away ; if still more closely set, 

 such stars will appear as a brighter nebulosity, even when 

 at a more moderate distance ; and a number of such stars 

 very closely set indeed will appear as a very bright 

 nebulosity even at a small (relative) distance. But 

 wheresoever set beyond the distance at which nebulosity 

 results, a star-cluster will appear neither brighter nor 

 fainter, only larger when nearer and smaller when farther 

 away. 



Thus when we see a bright milky nebulosity in a rounded 

 region (the shape showing that we have not to do with 

 enormously long ranges of stars in the direction of the 

 line of sight), we know that we have before us closely-set 

 stars, not stars strewn like those which form our constella- 

 tions. We know that the stars in Cassiopeia for instance 

 could never form a nebulous group such as the Pleiades 

 appears to weak eyesight, or the beautiful cluster in the 

 sword-hand of Perseus to the keenest vision. For we 

 know that long before the stars in Cassiopeia had ap- 

 proached near enough to each other,— through the reces- 

 sion of the group,— to coalesce, they would have disappeared 

 wholly from view. Nor would any further increase of 

 distance and the use of the telescope make any difference : 

 the telescope would increase the brightness of the stars 

 themselves as it increased the apparent distance between 

 them ; and at whatever distance the stars disappeared to 

 telescopic vision they would still be as far from coalescing 

 as when similarly disai)pearing to ordinary vision.* 

 So that the group of stars Ibrming the Pleiades is 

 altogether differently arranged from the group of as 

 many stars forming Cassiopeia ; the group forming the 

 Beehive (Pnv-icpe in Cancer) is again differently arranged, 

 the group in Perseus differently arranged still ; and in tine 

 each star-grouping is unlike its fellows, just as the family 

 of giant planets is unlike the family of terrestrial planets, 

 and that family again unlike the zone of asteroids. The 

 arrangements of stars are as varied as are the stars them- 

 selves unlike in size and glory : the architectuie of the 

 .stellar universe is as diverse as its materials. 



(To he continued.) 



* Perhaps I should rather say to ordinary vision corrected by a 

 jilasa just making the stars neat and well defined ; for there is 

 not one man in a thousand whoso view of a star group is not 

 to some degree improved by the use of an eye-glass just adapted 

 to correct the defects of his vision— defects scarcely noticeable 

 otherwise. 



THE WORKSHOP AT HOME. 

 Bv A Working Man. 



( Continued from p. 480 of Vol. VI.). 



OUR last piece of work was a set of bookshelves. I 

 now propose to show how to construct an equally 

 useful piece of furniture (if that is the right way of 

 describing it) : I mean a kind of wardrobe cupboard in a 

 bedroom recess. Fig. 33 is a plan of our recess — i.e., a 



Fig. 33, 



view of its shape as it would be presented to an eye in the 

 ceiling over it. I will suppose it to be 4 ft. 6 in. in 

 extreme width, and 1 ft. deep — common dimensions 

 enough, and this we are going to fit up as shown in Fig. 

 34, which represents our cupboard with the doors and their 



Fig. 34. 



frame removed. These figures are drawn to the scale of 

 half an inch to the foot, whence anyone, by the aid of a 

 divided rule, may see that the whole enclosure is to be 

 seven feet high. Of this we shall only utilise 6 ft. 1 in., the 

 remaining 1 1 in. being occupied by a more or less orna- 

 mental top. Now, we will use the wall itself in the recess 

 for the back of our cupboard ; but to the wall, on each side 

 above the skirting-board, must be securely nailed pieces of 

 board, s s, 101 in. wide, 1 in. thick, and of sufficient length 

 to make up, with the thickness of 1 in. board, 1 1, the entire 

 height of 7 ft. from the ground. Half-way between the.se 

 side pieces a piece of 1'. in. board, (/, must be fixed, acting 

 at once as a partition to diviJe the cupboard, and a stop, 

 against the front edge of which the closed doors will abut, 

 and into which a very simple form of bolt to hold them may 

 be fastened. The reader by this time will not need any 

 instruction in the art of sawing-out the planking, planing 



