Sept. 22, 1882/ 



• KNOWLEDGE • 



275 



ours than that of Mars, the four planets -which travel 

 nearest to the sun. 



But it will be convenient for us to consider at present 

 only the paths of our earth and Venus. 



Tip. 2. — The paths of Venue and the Earth around the Sun. 

 (On lh; scale of this fig^ire the Sun's diameter would be little more 

 than the thickness of the circles, represcntinsj the orbits of 

 Venns and the Earth. Venus and the Earth would be scarcely 

 discernible points.) 



Fig. 2 shows the shape and size of the paths of Venus 

 and the earth, S being the sun, the inside circle (with eight 

 little globes shown upon it) being the path of Venus, and 

 the outside circle the path of the earth. The earth takes 

 a year going round her path, while Venus goes round hers 

 in about seven months and a half, so that just as the two 

 hands of a clock going round at different rates come to- 

 gether at regular intervals, so Venus and the earth come 

 at regular intervals on a line with the sun, as shown at E 

 and Vj ui Fig. 2. But it will be easier to see what changes 

 must happen in the appearance of Venus, if we suppose 

 the earth to stay still as at E, and Venus to go round from 

 the position V, to all the other places V,, V,, Ac, shown 

 in the figure. It takes her about nineteen months to get 

 tlirough all these changes. When she is at V ^ she is very 

 far away, as the figure shows. Her bright face — that is, 

 the face the sun shines on — is turned towards the earth 

 full front, and the face she shows is therefore like 1 in 

 Fig. .3. She goes on to V„, drawing nearer, and turning a 

 small part of her dark half towards the earth ; so she looks 

 as 2, Fig. ;>. At V^ she is still nearer, and turns still more 

 of her dark half towards the earth ; looking like 3, Fig. 3. 

 At V^ she turns rather more than half her dark side 

 towards the earth, and looks like 4. At this time she 

 looks much brighter than when she was on any part of the 

 path from V, to V^. But now she draws up to the place 

 V , where her dark side is turned fully towards the earth. 

 Her face is like the horned moon during this part of her 

 course, but grows larger and larger, until when she is at 

 V „ it would be as large as .') in Fig. 3, if it could be seen. 

 But at this time it is out of sight, just as the moon is 

 before she shows as a new moon. Afterwards Venus goes 

 through the same changes, but in the reverse order, getting 

 smaller and smaller, but turning more and more of her 

 bright face towards us, as shown at 6, 7, 8 and 1, Fig. 3. 



Remembering that Venus takes nineteen months in passing 

 through all these changes, we see how it is that for about 

 seven months she gets brighter and brighter as an evening 

 star (this is while she is moving from near V^ toV^). 

 She then continues about a month more as an evening 

 star, but growing fainter (while she is moving from V ^ to 

 near V J. After this she becomes a morning star, growing 

 brighter for a month or so (while she is moving from near 

 Vj to Vg). And lastly, for eight months more, remaining 

 a morning star, she gets gradually fainter (while she is 

 moving from V^ to VJ. 



When Venus is observed without a telescope, she always 

 looks like a bright point of light, because she is so far from 

 us. But with a telescope, even a small one, the changes of 

 shape and size shown in Fig. 3 can be easily seen. They 

 were first seen by Galileo, the great Italian astronomer, ia 



•f f o 



Fig. 3. — Showing the Phases of Venus. 



the year 1610. If we could only see Venus's bright face 

 instead of her dark one, when she is nearest to us, we 

 could learn more about her ; but as it is, Venus cannot be 

 seen at all when nearest, and the more of her bright face 

 she turns towards us the farther away she gets. Yet we 

 have learned many interesting facts about her, and a few 

 which no one ever could have thought we should learn. 



Venus looks very beautiful to us, but our earth must 

 look far more beautiful to creatures li\'ing on Venus. For, 

 as is seen from Fig. 2, when Venus is nearest to the earth, 

 and turns her dark side towards us, the earth turns her 

 bright face to Venus. If ^'enus looks so bright as she 

 does when only turning towards us a small half-face like 4 

 orG (Fig. 3), and when shining on a bright sky, how glorious 

 must the earth appear when turning a bright disc as large 

 as 5 (Fig. 2), toward Venus, and shining on a black sky 1 

 For observe : when Venus is at V,, Fig. 1, the earth E is 

 on that side of her which is just opposite the sun. The 

 earth is therefore seen at midnight. So that, beautiful as 

 our sister-world looks to us, our own world looks still more 

 beautiful to Venus. It shines at midnight in her sky as a 

 star far brighter than our star of morning and evening, 

 and close by it the moon must bo quite clearly seen, now 

 on one side, now on the other. One cannot but wonder 

 whether there are creatures on Venus who admire this 

 beautiful sight in their skies, or try to find out if that 

 distant world, our own earth, is the abode of living 

 creatures. 



{To be coyi(i7iued.) 



ELECTRICAL ENGINEERING. 



THE unusual activity which has of late pervaded 

 electrical circles has, as might naturally bo expected, 

 opened the eyes of many fathers to the fact that a field 

 promises soon to open, if it be not already opened, in 

 which there will be free scope for those who devote their 

 energies to it with a view of making it remunerative. 

 With so many over-crowded professions before him, on 

 electrician's prospects are certainly not tlie poorest among 



