660 



SCIENCE. 



[Vol. II., No. 41. 



WUUKLY SUMMARY OF THE PROaRESS OF SCIENCE. 



ASTRONOMY. 

 " Rings of'Saturn. — Mr. William B. Taylor recalls 

 ftttention to the announcement made by Otto Struve 

 in 1851, tbat tbe'observations of two bundred years 

 sbowed tlie rings of Saturn to be widening, and tbe 

 inner edge of tbe inner bright ring to be approaching 

 tlie body of the planet. Later observations tend in 

 tbe same direction; and, though tberemay have been 

 unintentional exaggeration in Struve's numerical re- 

 sults, there seems little reason to question the gen- 

 eral fact. 



Accepting the only tenable theory of the rings, — 

 that they are composed of discrete particles, each 

 revolving in its own orbit, — we may, by Kepler's 

 law, compute the period of rotation of any part of 

 the ring. Assuming the period of the inner satellite 

 (Mimas) to be 22 b. .37^ m., the computed period of the 

 outer edge of the ring is 14 h. 30 m. ; of the dividing-' 

 stripe, 11 h. 20 m. ; of the inner edge of tbe bright 

 ring, 7 h. 12 m. ; of the inner edge of tbe dusky ring, 

 5 h. 45 m. ; and of the ring as a whole (supposed 

 solid), about 10 b. 50 m. The period of the planet 

 is 10 h. 14 m. 



With the complex perturbations induced by tbe 

 exterior satellites, it is evident tbat no particle of the 

 ring can revolve in a circular orbit; and it follows, 

 that, in a space so crowded with particles as to give 

 a continuous light, there must be much interference. 

 Whether the collisions at intercepting orbits result in 

 beat or in disintegration, they necessarily tend to a 

 degradation of motion, and hence to a shortening 

 mean radius-vector and a diminishing period. 



It thus appears that Struve's conclusions, based 

 on observation, have a rational theoretic basis. The 

 rings are falling toward the planet, and will event- 

 ually be absorbed. Indeed, on the generally received 

 meteoric theory of their constitution, it is impossible 

 to regard their present condition otherwise than as an 

 evanescent phase of a progressive evolution. 



Mr. Taylor points out tbat the relation between 

 tbe rotation periods of tbe planet and the ring, and 

 the relation between the rotation periods of Mars 

 and its satellites, not only fail to impeach the nebular 

 hypothesis, as some have supposed, but even fail to 

 be anomalous. 



If tbe planet had a velocity of rotation equal to 

 that of a satellite revolving at its surface, it could 

 not approach the spherical shape. And, tbe concrete 

 form having once been assumed, tbe rate of rotation 

 must necessarily and continuously diminish through 

 the influence of solar tides, until eventually the plane- 

 tary day and year are identical. — (Phil. soc. IVash- 

 ington; meeiiiiff Oct. 13, 1883.) [355 



ENGINEERING. 

 Emery's U. S. testing-machine, WatertoTvn 

 arsenal, Mass. — This machine is described from 

 general and detailed drawings furnished by the de- 

 signer. Tbe machine excels in strength, capacity, 

 durability, accuracy, and sensitiveness. The demand 



is said to have been : 1°. A machine to test to 800,000 

 pounds, and so delicate that it would test a single 

 horse-bair. 2°. Attachments enabling it to seize and 

 hold uninjured, while applying such loads, all usual 

 sizes and shapes of specimens. 3°. Safety ag.iiust 

 injury by shocks of recoil. 4°. Accessibility of 

 samples and straining parts, while in operation, for 

 purposes of measurement and inspection. 5°._ Small 

 cost of operation. 



The machine was tested, when finished, to 1,000,000 

 I)Ounds, and iinder smaller loads, ranging down to a 

 single horse-bair, with success; and was accepted by 

 the U.S. board appointed to test iron, steel, and other 

 metals. The loads are .ipplied by a hydraulic press; 

 and the weighing is done through reducing-pressure 

 cushions and water-columns terminating at a point 

 of connection with weigh-beains without knife-edges 

 and having extraordinary sensitiveness. Mr. Emery 

 is constructing smaller machines, and scales and 

 pressuje gauges involving the nicer and more re- 

 markable devices introduced in the large machine, 

 at the works of tbe Tale & Towne company, at Stam- 

 ford, Conn. Mr. Emery's inventions are expected to 

 aid effectively in securing a more exact knowledge of 

 the properties of the materials of construction, and 

 of their value in structures. — {Amer. mach., July 

 21. ) n. n. T. [356 



Engineering of the great statue of Liberty. 

 — Mr. Ch. Talausier describes tbe details of en- 

 gineering involved in the design of Barlholdi's 

 statue of ' Liberty enlightening the world.' The 

 plan was conceived by M. Bartboldi in 1871, while 

 en voyage for the United States. On the hundredth 

 anniversary of the declaration of independence, 

 France offered the great statue to tbe United States. 

 It was accepted, is now nearly completed, and prepa- 

 rations for its erection on Bedloe"s Island, in New 

 York harbor, are being made. The statue is of copper, 

 carried and strengthened by an inner skeleton of iron. 

 One arm, carrying the torch, was sent to the Cen- 

 tennial exhibition at Philadelphia in 1876, and has 

 since been on exhibition in New York. The sculptor 

 first made a model 2.11 m. high, which was then 

 copied on a fourfold scale; and the statue was con- 

 structed from this model in sections by similarly 

 enlarging each section. For each piece, a ' centre,' 

 or mould, was made of wood, on which the copper 

 could be worked and fitted. The sheet-copper epi- 

 dermis of the statue is composed of 300 pieces, and 

 weighs 80,000 kilograms (178,000 lbs.). The iron 

 frame weighs 120,000 kilograms (204,000 lbs. ). When 

 finally erected, the sheets of copper will be riveted 

 together with copper rivets 5 mm. in diameter 

 (0.2 in.), and spaces 25 mm. (1 in.) apart. The iron 

 skeleton is to be secured to tbe foundation at four 

 points by 12 foimdation-bolts 0.15 m. (G in.) in diam- 

 eter, and extending 15 m. (40.7 ft.) into the masonry. 

 The variation of form and dimensions, with varying 

 temperature, is provided against by the elasticity of 

 every part ; and corrosive action is to be checked by 



