517 



SCIENTIFIC SIDE-LIGHTS 



Perception 

 Perfection 



than the absolute quality or quantity of a 

 given sensation is its ratio to whatever other 

 sensations we may have at the same time. 

 When everything is dark, a somewhat less 

 Jark sensation makes us see an object white. 

 Helmholtz calculates that the white marble 

 painted in a picture representing an archi- 

 tectural view by moonlight is, when seen 

 by daylight, from ten to twenty thousand 

 times brighter than the real moonlit marble 

 would be. JAMES Psychology, vol. i, ch. 9, 

 p. 231. (H. H. & Co., 1899. j 



2545. PERFECTION, MATHEMAT- 

 ICAL, OF HONEY-BEE'S CELL [As stated 

 by Dr. Reid] there are only three possible 

 figures of the cells which can make them all 

 equal and similar, without any useless in- 

 terstices. These are the equilateral tri- 

 angle, the square, and the regular hexagon. 

 Mathematicians know that there is not a 

 fourth way possible in which a plane may 

 be cut into little spaces that shall be equal, 

 similar, and regular, without useless spaces. 

 Of the three figures, the hexagon is the most 

 proper for convenience and strength. Bees, 

 as if they knew this, make their cells regu- 

 lar hexagons. 



Again, it has been demonstrated that, by 

 making the bottoms of the cells to consist 

 of three planes meeting in a point, there is 

 a saving of material and labor in no way 

 inconsiderable. The bees, as if acquainted 

 with these principles of solid geometry, fol- 

 low them most accurately. It is a curious 

 mathematical problem, at what precise 

 angle the three planes which compose the 

 bottom of a cell ought to meet, in order to 

 make the greatest possible saving or the 

 least expense of material and labor. This 

 is one of the problems which belong to the 

 higher parts of mathematics. It has ac- 

 cordingly been resolved by some mathema- 

 ticians, particularly by the ingenious Mac- 

 laurin, by a fluctionary calculation, which is 

 to be found in the Transactions of the 

 Royal Society of London. He has deter- 

 mined precisely the angle required, and he 

 found, by the most exact mensuration the 

 subject would admit, that it is the very 

 angle in which the three planes in the bot- 

 tom of the cell of a honeycomb do actually 

 meet. ROMANES Animal Intelligence, ch. 4, 

 p. 171. (A., 1899.) 



2546. PERFECTION, MECHANICAL, 

 OF INSECT'S WORK Larva Spinning Its 

 Shroud. For some time Mr. Agassiz has 

 been trying to get living specimens of the 

 insect so injurious to the coffee-tree, the 

 larva of a little moth akin to those which 

 destroy the vineyards in Europe. Yester- 

 day he succeeded in obtaining some, and 

 among them one just spinning his cocoon on 

 the leaf. We watched him for a long time 

 with the lens as he wove his filmy tent. He 

 had arched the threads upwards in the cen- 

 ter, so as to leave a little hollow space into 

 which he could withdraw; this tiny vault 

 seemed to be completed at the moment we 



saw him, and he was drawing threads for- 

 ward and fastening them at a short distance 

 beyond, thus lashing his house to the leaf, as 

 it were. The exquisite accuracy of the work 

 was amazing. He was spinning the thread 

 with his mouth, and with every new stitch 

 he turned his body backward, attached his 

 thread to the same spot, then drew it for- 

 ward and fastened it exactly on a line with 

 the last, with a precision and rapidity that 

 machinery could hardly imitate. AGASSIZ 

 Journey in Brazil (extract from Journal of 

 Mrs. Agassis), ch. 3, p. 117. (H. M. & Co., 

 1896.) 



2547. PERFECTION OF APPARATUS, 

 IMPORTANCE OF Velocity of Light Error 

 as to Sun's Distance Vitiated Early Meas- 

 urements A Terrestrial Distance, That Can 

 Be Surely Measured, Now Made the Basis 

 of Calculation. Fizeau, and quite recently 

 Cornu, employing not planetary or stellar 

 distances, but simply the breadth of the city 

 of Paris, determined the velocity of light: 

 while Foucault a man of the rarest me- 

 chanical genius solved the problem with- 

 out quitting his private room. Owing to an 

 error in the determination of the earth's 

 distance from the sun, the velocity [192,500 

 miles per second] assigned to light by both 

 Romer and Bradley is too great. With a 

 close approximation to accuracy it may be 

 regarded as 186,000 miles a second. [From 

 a discussion of all observations in 1891, 

 Professor Harkness found 186,337 -H 49.722 

 miles (J. E. Gore, in Flammarion's" 7 ' Popu- 

 lar Astronomy," p. 318) . Flammarion takes 

 300,000 kilometers, or 186,414 miles, as an 

 accurate statement " in round numbers."] 

 TYNDALL Lectures on Light, lect. 1, p. 23. 

 (A., 1898.) 



2548. PERFECTION OF EARLY IN- 

 STINCT Common Spiders. Mr. Blackwall, 

 speaking of British spiders, says : " Com- 

 plicated as the processes are by which these 

 symmetrical nets are produced, nevertheless 

 young spiders, acting under the influence of 

 instinctive impulse, display, even in their 

 first attempts to fabricate them, as consum- 

 mate skill as the most experienced indi- 

 viduals." ROMANES Animal Intelligence, 

 ch. 6, p. 216. (A., 1899.) 



2549. Trap-door Spiders. 



Speaking of trap-door spiders, Moggridge 

 says: 



" I cannot help thinking that these very 

 small nests, built as they are by minute 

 spiders probably not very long hatched from 

 the egg, must rank among the most mar- 

 velous structures of this kind with which 

 we are acquainted. That so young and 

 weak a creature should be able to excavate 

 a tube in the earth many times its own 

 length, and know how to make a perfect 

 miniature of the nest of its parents, seems 

 to be a fact which has scarcely a parallel In 

 Nature." ROMANES Animal Intelligence. 

 ch. 6, p. 217. (A., 1899.) 



