534 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



sailing with a uniform movement clears a given space with 

 the least possible fall when the work of suspension is sensibly 

 equal to the work of translation : the plane of the wings then 

 bisects the angle formed by the horizon and the direction 

 of movement, and the latter angle is itself a minimum. 



From these principles (which apply to birds, and not nec- 

 essarily to insects), Penaud deduces most of the known char- 

 acteristics of the flight of birds. For insects, as w^ell as for 

 fishes, the modes of propulsion involve quite different princi- 

 ples of mechanics. IJAeronaiite^ January^ 1873. 



LONG BALLOON YOYAGES. 



The proposal to build a large balloon, and start on a Yoy- 

 age from America to England, has called forth an excellent 

 letter from the veteran balloonist, Samuel A. King, whose 

 strenuous efforts and great personal sacrifice in the attempt 

 to make the balloon the means of yielding reliable scientific 

 results have placed him among the foremost of those who 

 have devoted themselves to such work in this country. 



In reference to crossing the Atlantic, Mr. King writes : " I 

 do not know of a single scientific authority Avho indorses any 

 theory of a direct current moving continually from west to 

 east at any height. The probable direction of the upper cur- 

 rent would be from Boston over New BrunsAvick and the 

 southern coast of Greenland into the Arctic Ocean." 



The longest voyages with the greatest balloons ever made 

 have never been equal to one entire day. The balloon can 

 not retain its gas a longer time because of the overflow at 

 the neck. Even if it could be maintained in the high w^est- 

 ern current, the time required to reach Europe must far ex- 

 ceed the two or three days promised by the projectors of the 

 enterprise, since the average velocity of all the very high as- 

 cents is not greater than twenty miles an hour, to say nothing 

 of the fact that they move in every other direction than the 

 one needed for a trip across the Atlantic. In reference to 

 the uses of the balloon for meteorological and jfliysical obser- 

 vations, it may be stated that Mr. King has made over one 

 hundred and eighty balloon v.oy.ages, in several of which he 

 has traveled remarkable distances. A brief synoj^sis of these, 

 giving the direction of tlie upper and lower currents, with 

 other data, was read by him before the Washington Philo- 



