570 



SCIENCE, 



[Vol. VI., No. 151. 



other hand, is best for the case of the heavily 

 plated, lightly loaded ship. The heavier the armor, 

 the shorter and broader, j)roportionately, must be 

 the hull chosen to do the best work. The fact that 

 the shorter and broader, though for a given dis- 

 placement the lighter, ship demands greater 

 engine-power, brings another complication into 

 the problem ; and it is for the naval architect and 

 engineer to seek the form which, on the whole, 

 will be best for his purpose. On the whole, it is 

 found that, for war-vessels, the heavier the armor 

 to be carried, the fuller the form to be chosen : 

 in other words, the value of a ship for purposes of 

 war is not to be judged at all by the magnitude 

 of the so-called ' constant of performance ' (cube 

 of the speed, multiplied by the two-thirds power 

 of the displacement, divided by the indicated 

 horse-power). A ship with a high coefficient may 

 be a very bad vessel for war purposes, even though 

 easily propelled through the water. This is a very 

 important principle in naval architecture, and is 

 the more to be kept in view from the fact that 

 it has been customary for many years to judge the 

 value of a design by the magnitude of this con- 

 stant or some similar quantity. The application 

 of a correct method of comparison shows the 

 Belerophon, a short ship of 800 feet length, to be 

 superior as a war- vessel to the Minotaur, — a sliip 

 of 400 feet length, and of much finer form. The 

 smaller ship was ' handier,' attained the same 

 speed, carried an equal battery better protected, 

 had the same engine-power, and cost less than 

 three-quarters as much as the larger. But her 

 coefficient was about 15 per cent lower. This 

 comparison effected a revolution in the naval 

 design of Great Britain. The later iron-clads are 

 built with a length only about five times the 

 breadth, though steaming 16 and 17 knots. 



It is found, on carrying out the investigation, 

 that the short, broad ship, which should be given, 

 nevertheless, fine ' entrance' and ' run,' may often 

 be subject to less resistance than a rival craft of 

 greater length and less beam. This was shown by 

 Froude's experiments on the Ajax and a rival form. 

 The magnitude and position of the ' bow wave ' 

 relative to the stern of the ship is one of the im- 

 portant modifying conditions. Should that wave 

 take the right position, the resistance may be 

 much less than where it comes in the wrong place. 

 The action of the screw, in reUeving the pressure 

 of the water under the stern, is another serious 

 consideration. Froude found, that, if it could be 

 placed one-fourth or one-third the ship's beam 

 from the stern of the vessel, the resistance to 

 propulsion would be very much decreased. The 

 introduction of a lengthened middle body may 

 or may not aid ; but no principle or formula 



has yet been found to determine what the effect 

 will be. 



Of the three principal elements of resistance, 

 the friction of the skin of the ship, the wave-mak- 

 ing effect, the eddy resistance, the first is usually 

 the greatest. In very fast vessels the second and 

 third may approximate to equality with the first. 

 At low speeds the friction may be nine-tenths 

 the total : at high speeds, such as now are becom- 

 ing common, the frictional resistance may become 

 as low as one-half the total. Comparing war- 

 vessels, it is seen that fine-lined ships having thick 

 armor would require to be of enormous length, 

 size, cost, and power, while the same offensive and 

 defensive power may be obtained in full-lined 

 ships at much less sacrifice of all desirable quali- 

 ties. 



No insuperable obstacles exist to-day to the 

 production of armored war-vessels capable of 

 defying all the ordnance of the world, and of 

 carrying their own armament at a speed of 18 or 

 20 knots into the waters of any enemy. The cost 

 of such vessels has become so great, however, that 

 progress in this direction has apparently nearly or 

 quite ceased for the present. The engineer and 

 naval architect is prepared to do his part of the 

 work whenever the nation shall call upon him. 



This was the closing lecture of a course cover- 

 ing the general subject of hydromechanics, and 

 was considered a very fitting final address. 



MEDICAL MISSIONARY WORK IN CHINA. 



In 1881 Dr. Elizabeth Reifsnyder graduated in 

 medicine from the Woman's medical college of 

 Pennsylvania. Two years afterward she went as 

 a medical missionary to Shanghai, where she is in 

 charge of a new and handsome hospital. On Oct. 

 25, 1884, she performed the first ovariotomy ever 

 done in northern China. The subject was thirty- 

 one years of age, and travelled about five hundred 

 miles to see Dr. Reifsnyder. The tumor weighed 

 thirty-three pounds, and eleven days after the 

 operation the patient sat up. 



A successful operation like this soon made her 

 famous, and the Chinese published accounts of 

 the case. From one of these pamphlets the an- 

 nexed cut is reproduced. It is evidently an ideal 

 sketch by a native artist of great capacity, and 

 vies in its amusing misrepresentation with some 

 of the manufactured conversations of the modern 

 interviewer. 



It is al fresco ; and evidently two passers-by — 

 an Englishman and a Scotchman, to judge by 

 their looks — have been attracted by the sight, and 

 are watching it from the street. But the doctor's 

 attitude and dress are the most amusing things in 



