AQUARIUM 



463 



The fringetail telescope is just as in- 

 consistent a creation as would be a 

 long-tailed bulldog on a short-haired 

 collie. In telescopes, let us again have 

 colors and eyes, and in fringctails, fins 

 and form. 



Goldfish Pull Up Plants. 



An inquiry from a member of The 

 Agassiz Association as to the best 

 method of stopping goldfish pulling up 

 plants was referred to William T. 

 Innes, Philadelphia, Pennsylvania. 

 He has written in reply as follows: 



"It is generally large, single-tail 

 goldfish that pull up plants. I know of 

 no way of breaking up the habit. The 

 best thing to do, if one does not wish 

 to dispose of the fish and get smaller 

 ones, is to plant giant Sagittaria and 



plant it deeply, spreading out the roots 

 well. The broad, strong leaves of 

 this plant are more difficult for the 

 fish to get hold of and the mots are 

 very firm when once established. 



"Fish sometimes learn they can up- 

 root plants that have not been planted 

 thoroughly, and after they once get 

 the idea the only way to get ahead of 

 them is to go beyond their strength. 

 Plant giant Sagittaria down against 

 the bottom and cover the roots with 

 one and one-half inches of sand. 



"Do not use seashore sand. It 

 packs too hard and the plants do not 

 prosper. Silver sand as used for bird 

 cages is pretty but river sand will do, 

 or any kind that is not very fine. Bird 

 sand is clean and white and where the 

 quantity required is not large, the out- 

 lay is well expended." 



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DQMINIQN QVEPJ 

 PHYSICAL NATURE* 



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How a Motor-Boat Engine is Made. 



Description of a Two-Cycle 



Motor. 



BY EDWARD F. BIGEEOW, SOUND BEACH, 

 CONN. 



A motor-boat is always fascinating. 

 It glides through the water so swiftly 

 that the speed appears to be the work 

 of magic. Even the regular "chug, 

 chug, chug" of the engine seems more 

 like the voice of some mysterious, 

 aquatic animal than like the sound of 

 other engines, for, of all vessels, the 

 motor-boat has its power the most con- 

 cealed, the greater part of the engine 

 usually being placed below the Mooring 

 of the boat, where it is invisible and out 

 of the way of the passengers. Sails, 

 walking beams or paddle wheels are 

 conspicuous, but a motor-boat, with 

 none of these in sight, seems to be 

 towed by some mysterious, submarine 

 animal. 



>!STW^ 



From the mechanical point of view 

 a motor engine on account of its regu- 

 lar sparking from an electric current 

 and its rhythmical gas explosions 

 is interesting. For these reasons our 

 readers may like to know how a motor 

 engine is made and how it operates. 



It consists primarily of an iron box, 

 known as a cylinder, within which 

 plays back and forth a "plunger," 

 known as the piston attached to the 

 piston rod" — the whole being known 

 as a piston and rod. 



The backward and forward move- 

 ments of this piston are produced by 

 explosions of compressed gasoline 

 vapor, mixed with air, the explosions 

 being caused by an electric spark, and 

 the spark made in the gas in the cylin- 

 der by the sudden breaking of the elec- 

 tric current through each revolution of 

 the fly wheel. The explosion of this 



