♦ KNOWLEDGE ♦ 



A FAST STEAM- YACHT. 



FOR more tlian twenty-two years tlie side-wheel 

 steamboat Mary Powell has been recognised as the 

 fastest boat on the Hudson River ; she makes an average 

 of twenty miles an hour, and according to a pamphlet 

 issued by the owners, "in the year 1882, she ran at the 

 very fast rate of 26 miles an hour between Milton and 

 Poughkeepsie, making the four miles in nine minutes." 

 Boats of all sorts of shapes, big and little, side-wheels 

 and propellers, have unsuccessfully attempted to wrest 

 from her the well-earned title of Queen of the Hudson. 

 But on June 10 she was badly beaten in a long run 

 by a small steam-yacht of very insignificant appearance. 

 The run was from this city to Sing Sing, a distance of 

 30 miles, and was made by the steam-yacht Stiletto in 

 one hour and fifteen minutes, the Mary Powell, on her 

 regular trip to Rondout, being beaten about two miles. 



The Stiletto was designed and built by the Herreshoff 

 Manufacturing Co., of Bristol, Rhode Island. She is 

 94ft. long over all, 90ft. on the water-line, and lift, 

 beam. The hull is double planked, and sharp at both 

 ends, the cvu-ves extending far toward the centre. A 

 slightly arched deck covers the whole boat. Forward is 

 a pilot-house sufficiently large to serve as a commodious 

 cabin. Owing to the extremely small space taken up by 

 the engine and boiler rooms, there is ample room for 

 comfortable quarters for the crew and state-rooms for the 

 owner, guests, and ofiicers. Power is furnished by a 

 compound condensing-engine of 12-inch stroke and 

 cylinders 12 and 21 in. in diameter; the engine is sup- 

 plied by a sectional water-tube boiler, in which steam 

 can be got up quickly, and which is calculated at 450 

 horse-power. Although this boiler is similar in principle 

 and operation to those of the regular HerreshofE type, it 

 varies greatly in construction, the tubes being arranged 

 horizontally in sets immediately over the fire — each set 

 being at right angles to those just above it. Exhaust 

 steam is led to a surface condenser. An ordinary pump 

 takes the water from the condenser, forces it into the 

 upper set of boiler tubes, through the boiler to a sepr.- 



rator located in front of the boiler, and to which the 

 steam-pipe is connected. The boiler will work safely 

 with 1601b. of steam, but in the race with the Mary 

 Powell it was only found necessary to use from 120 to 

 125 lb. The fire-box is 6^ ft. square. 



The screw is four-bladed, 4 ft. in diameter, and 6 J ft. 

 pitch. At the stern the boat draws 4| ft., and at the 

 bows 3 ft. "We may notice that there are now building 

 at the yards of Yarrow & Co., England, two torpedo 

 boats which are expected to run, when light, at the rate 

 of 24 knots an hour, or nearly 28 miles. The Stiletto 

 must do better than 25 miles an hour before she can 

 claim the broad title of the fastest boat in the world. — 

 Scie7itific American. 



THE RUDDY ECLIPSE OF THE 

 MOON. 



By Richard A. Pkoctoe. 



(Continued from page 47.) 



IF we consider what really happens when (as supposed 

 to be seen from the moon) the sun is passing behind 

 the earth, and therefore the earth's shadow is thrown on 

 the moon, we shall readily understand the increase of the 

 earth's effective shadow-throwing diameter by about one- 

 sixtieth part, — a circumstance which some so strangely 

 misinterpret,* that they appear to imagine a range of 

 60 or 70 miles of our atmosphere above the sea-level to 

 play a part in determining the phenomena of a total lunar 

 eclipse ! 



Suppose ESE', Fig. 1, tlit 

 outline of the earth E C E' j 

 of the sun's disc, Z-K/.-', l\. 

 the advancing edge of the cai 

 the summit of geometrical ti 



I the 





* The mistake is very commonly made of attribnting this inc 

 to the earth's atmosphere. In reality the earth's atmospher 

 nothing t J do irith ic. 



