for future reference."

[Illustration: _Fig. 16. Slip knot._]

[Illustration: _Fig. 17. Overhand knot._]

[Illustration: _Fig. 18. Flemish Loo._]

[Illustration: _Fig. 19. Fig. 8 knot._]

[Illustration: _Fig. 20. Stevedore knot._]

[Illustration: _Fig. 21. Bowline knot._]

[Illustration: _Fig. 22. Double knot._]

[Illustration: _Fig. 23. Weaver's knot._]

[Illustration: _Fig. 24. Carrick bend._]

[Illustration: _Fig. 25. Reef bend._]

He then proceeded to make the knots, and continued: "The seven knots
(Figs. 16 to 22, inclusive) are made at the ends of the rope, as you
will notice, and are the forms used to attach the rope to an object. In
the next three forms two ropes are attached to each other, and are
usually called 'bends' (Figs. 23, 24, 25).

"Then, in addition to that, the sailor has several ways of attaching the
rope by a hitch around a standard, or other object. Look at these two
forms (Figs. 26, 27). Look at the boat knot, where the hitch is made in
the rope itself; and the sheet bend toggle, where the ends of two ropes
are attached together to a standard or cleat. And now I am making what
are called hitches, and the three forms (Figs. 28, 29, 30) are the best
examples."

[Illustration: _Fig. 26. Boat Knot._]

[Illustration: _Fig. 27. Sheet bend and Toggle._]

[Illustration: _Clove Hitch Fig. 28._]

[Illustration: _Half Hitch Fig. 29._]

[Illustration: _Timber Hitch Fig. 30._]

Thus the conversation drifted from one subject to another, covering a
variety of interesting topics. George reminded the Professor that he had
not yet explained to them what the spectroscope was, and its uses. He
laughingly responded:

"That instrument is one of the most wonderful in all the ranges of human
discoveries. By its means the elements of substances are determined, and
the composition of the heavenly bodies are ascertained."

"In what way is it done?"

"Simply by using light as the agency."

"Is it like a telescope?"

[Illustration: _Fig. 31. The color Spectrum._]

"No; entirely different. It depends wholly on one thing, and that is the
breaking up or dividing the light that comes from an object. Let me make
this a little plainer. If a ray of sunlight is allowed to pass through
an orifice into a darkened room, and in the transit through the opening
it goes through a prism, or three-sided piece of glass, the light
produced on the opposite wall will show the seven colors of which
sunlight is com