390 ANNUAL OF SCIENTIFIC DISCOVERY. 



The feature to which Mr. Bond's attention has been particularly 

 directed is the spiral of the principal masses of light in this nebula ; 

 or* more correctly, the tendency to an arrangement in elongated 

 \visps or whirls, sweeping outward from the bright region of the Tra- 

 pezium. These peculiarities, which constitute the leading features 

 of this nebula, have heretofore escaped particular notice. Mr. Bond 

 describes the general aspect of the greater part of the nebula as that 

 of an assemblage of curved wisps of luminous matter, which, branch- 

 ing outward from a common origin in the bright masses in the vicinity 

 of the Trapezium, sweep towards a southerly direction. About 

 twenty of these convolutions have been distinctly traced, while others, 

 giving a like impression, are too faint or too intricate to be subjected 

 to precise description. It may, therefore, be properly classed among 

 " the spiral nebulas, " under the definition given by their first discov- 

 erer, Lord Rosse ; including in the term all objects in which a curvi- 

 linear arrangement, not consisting of regular re-entering curves, may 

 be detected. 



Among other interesting observations noticed by Mr. Bond in this 

 connection, is the disposition of nebulosity in the neighborhood of 

 groups of stars or of single bright stars, apparently in preference to 

 other localities ; an instance, perhaps, of the same distribution 

 which we see among the smaller stars in some parts of the heavens, 

 where they arrange themselves by preference in the neighborhood of 

 the brighter ones, the intermediate spaces being left comparatively 

 vacant. 



Bond's Isodynamic Escapement for Astronomical Clocks. An 

 isodynamic escapement for astronomical clocks, recently invented by 

 Mr. Richard C. Bond, of Boston, greatly contributes to the removal 

 of the small causes of error recognized as existing in the most perfect 

 time-keepers hitherto constructed; and thus confers an important 

 benefit upon astronomical science. Its principal peculiarities are, 

 that it entirely obviates the difficulty arising from the varying power 

 transmitted by the wheel-work, and also obviates the necessity of 

 guarding against what is called tripping, or the danger of two or 

 more teeth of the escapement wheel passing the pallets at once, when 

 only one is intended to ; thus causing the hands of the clock to gain 

 by jumps, in the most unreliable manner, even while the pendulum is 

 vibrating with perfect regularity. The construction of this escape- 

 ment has been made public by Mr. Bond, in a pamphlet, accompa- 

 nied by a diagram. 



THE PERIODICITY OF THE SUN's SPOTS. 



Mr. O. Reichenbach, of Norristown, Pa., communicates to Sim- 

 man's Journal the following paper on the cause of the periodicity of 

 the sun's spots, as determined by the observations of M. Schwabe, 

 of Dessau. (See Annual of Scientific Discovery, 1858, page 397.) 



The frequency of spots, in passing from maximum to minimum, 

 embraces, according to M. Schwabe, a period of about eleven 

 years. Now period by a primary cause oscillates by secondary 

 causes. The revolution of Jupiter, the largest planet, is 11.86 years. 

 There is affinity in these numbers. The maxima occurred in 1828, 



