April 27, 1SS3.] 



SCIENCE. 



335 



the time there was not wind enough to do more than 

 to swing the spider to the same angle from the verti- 

 cal that he was then making above the horizon. It 

 seemed the more surprising, as the spiders wei'e large, 

 and ought, by all the laws of gravity, to have fallen 

 to the earth at once. And what was their objective 

 point, aiming, as they did, for the clouds and stars? 

 But I content myself with the statement of the facts, 

 leaving to others the how, why, and whither. 



E T. QUIMBY. 



Hanover, N".H. 



Improvement of ■western pasture-land. 



In his article in Science, p. 186, Professor Shaler's 

 opening sentence, " that the greater part of the United 

 States west of the meridian of Omaha is unfit for 

 tillage," leaves a somewhat wrong impression. The 

 greater part of Nebraska is west of that meridian; 

 but nearly the whole state, as far as longitude 99"=', 

 produces crops of the cereal grains, grasses, corn, 

 fruit, and roots, more surely, even, than the middle 

 states. This area embraces 30,000 square miles. 

 - Large sections west of the 99th meridian produce 

 almost equally well, as onr statistics show. His sug- 

 gestions, however, apply to the proper management of 

 the grasses outside of this area, and are of very great 

 importance. 



A remarkable peculiarity of our Nebraska flora is 

 its changing character. While not confined to the 

 grasses, it is especially conspicuous among them. 

 When I first crossed this county (Lancaster) in 186.5, 

 buffalo-grass (Buehloe dactyloides) covered much of 

 the uplands. By 1871 nearly all of this species had 

 disappeared ; and its place was taken by blue-joints 

 (Andropogou furcatus, etc.), interspersed with Boute- 

 louas, Sorghum nutans, Sporobolus, etc. Again, in 

 1878, the blue-joints disappeared from entire town- 

 ships, and the Boutelouas usurped their place. Simi- 

 lar phenomena were observed in almost every county 

 in the state, and even in sections where settlements 

 had not penetrated. During the last two years Sor- 

 ghum nutans has been gaining in eastern Nebraska 

 over all other species. On the whole, the species 

 indigenous to moist regions have been gaining on the 

 buffalo-grasses to such an extent that the latter have 

 almost entirely disappeared east of the 100th meridi- 

 an, and from large areas fartlier west. In extreme 

 north-M'estern Nebraska, on tributaries of the Nio- 

 brara, I have obsei'ved, since 186.5, a remarkable 

 exchange of buffalo-grass for Boutelouas and other 

 grasses in different years.' This tendency, therefore, 

 is common, though not to the same extent, in the 

 drier as well as the raoister portions of the state. 

 When old Fort Calhoun, above Omaha, was occupied 

 by the military, twenty-five years ago, Kentucky 

 blue-grass was brought in baled hay to that post from 

 the south. It spontaneously took root, and spread in 

 every direction, and now it can be found on prairies 

 thirty miles away. Many of our farmers in eastern 

 Nebraska are looking to that species now for a grass 

 to give late fall and early spring pasturage. 



Under favorable conditions, the wild native grasses 

 produce a remarkable amount of hay. The blue- 

 joints range in productiveness from one to three tons 

 and more per acre. The latter large yield has been 

 realized even at the 99th meridian on the wide Elk- 

 horn-river bottoms. All the facts noted in the moist 

 as well as dry sections of the state confirm Professor 

 Shaler's theory; namely, that the natural conditions 

 on the plains are most favorable to a changing grass 

 vegetation, and that it is possible, through the agency 

 of man, greatly to improve on the native species. 



Samuel Aushet. 



Apparent attractions and repulsions of small 

 floating bodies. 



As I thought it worth while, in the interests of 

 clear teaching, to object (Science, i. p. 43) to certain 

 tilings in Professor John Leconte's explanation of 

 the ' AiJijarent attractions and repulsions of small 

 floating bodies,' ^ it seems my duty, now that Profes- 

 sor Leconte has replied (Science, i. p. 249) to my 

 criticism, to justify that criticism, or, failing iu |;hat, 

 to acknowledge my error. 



A statement in his explanation of the behavior of 

 two moistened floating bodies, to which I particularly 

 objected, was the following : " But when brought so 

 near that their meniscuses join each other, the radius 

 of curvature of the united, intervening, concave me- 

 niscus ... is less than that of the exterior concave 

 meniscuses, . . . and its superior tension acts upon 

 both bodies toward a common centre of concavity." 



The parts omitted from this sentence are merely 

 references to a diagram. Professor Leconte now 

 states that he should have said superior force- instead 

 of superior tension. I, however, objected to the 

 statement on quite other grounds. After quoting it, 

 I said, " We do not think physicists generally will 

 admit that a liquid film tends to draw a solid, to 

 lohich it is attached, toward the centre of concavity of 

 the film. Indeed, if this were so, the tendency of a 

 column of water raised between two floating bodies 

 by surface-tension would be to lift those bodies, 

 Similarly, a colunm of liquid sustained in a fine tube 

 would tend to lift the tube." 



* I have quoted myself thus at length, — using italics, 

 which I did not use before, — because Professor Le- 

 conte appears to understand me as denying that what 

 he calls the 'capillary forces' — such, for instance, 

 as the force exerted upon the enclosed air by the film 

 of a soap-bubble — are directed toward the centre of 

 concavity of the film. I spoke merely of the force 

 exerted upon the body to xchich the edge of the film 

 is atlaclied; and the force exerted by the film upon 

 such a body is certainly not directed toward the cen- 

 tre of concavity of the film. If we coil a rope round 

 a cask, and set a man to pull at each end of the rope, 

 the pressure on the cask will be everywhere directed 

 toward the centre of curvature of tlie coil: but the 

 pull on the men will not be toward the centre of 

 curvature of the coil ; it will be tangential to the coil. 

 In the same way, the action of a meniscus upon the 

 water beneath it, or the air above it, is directed to- 

 ward the centre of concavity of the meniscus ; but the 

 action of the meniscus upon the body to which it is 

 attaclied is tangential to the liquid surface, and per- 

 pendicular to the bounding edge of tlie meniscus. 



Professor Leconte, however, has cliQsen to make the 

 statement I have quoted above ; and to my criticism 

 thereon he replies, "Indeed, it is obvious tliat the 

 elastic reaction of the common meniscus, formed 

 when two such floating bodies are brought near to 

 one another, does not tend to lift them ; for the vertical 

 component of the capillary forces, directed toward 

 the centre of concavity, is exactly counterbalanced 

 by the weight of the adhering liquid elevated between 

 them, while tlie horizontal component is free to 

 draw them together." He makes a similar statement 

 concerning the action in a capillary tube. 



It is, indeed, obvious, that the weight of the water 

 must be sustained ; but how and where is this weight 

 applied to the floating bodies or to the tube ? If it is 

 applied by means of tiie surface-film, and at the line 

 where the bounding edge of that film meets the float- 

 ing bodies, or the wall of the tube. Professor Leconte's 



1 Amer. journ. sc, December, 1882. 



