Star-land : being talks with young people about the wonders of the heavens (1891)
Ball, Robert S. (Robert Stawell), Sir, 1840-1913 · London ; Paris : Cassell & Co. · leaf 173
we put them in. Next we take apiece of twine and tie the two ends together so as to form a 158 Star-Land. loop, which we pass round the two tacks (Fig. 53). Inthe loop I place the pencil, and then you see I move itround, taking care to keep the twine stretched. Thus Iproduce a pretty curve, which… … Fig. 53.—How to draw an Ellipse. and a parabola (Fig. 54). Elliptic curves can be made verynearly circles by putting the two tacks close together, orthey can be made very long in comparison with their width.They are all pretty and graceful figures, and are often usefulfor ornamental work. The…
Astronomy
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