142 



SCIENCE. 



recurring with great regularity. Examples, /3 Persei and 

 (5 Cephei. 



In order to avoid all prejudice, the present discussions 

 are made to depend entirely on the work of previous 

 observers, while awaiting the completion of more pre- 

 cise observations now in progress at Harvard College 

 Observatory. 



An investigation was given in the article referred to 

 above, of stars of the fourth class. It was shown that in 

 the case of Persei at least, the observed variations 

 could be very satisfactorily explained by the theory that 

 the reduction in light was caused by a dark eclipsing 

 satellite. 



Variables of the third class are considered in the 

 present paper. Perhaps the most natural supposition of 

 the variability of a star of short period, is that it is due 

 to rotation around its axis. The difference in brightness 

 of the two sides of a star, which such an explanation de- 

 mands, may be due to spots like those of our sun, to 

 large dark patches, or to a difference in temperature. 

 The theory that variation is due to the absorption of a 

 rotating mass of gas, does not appear probable for stars 

 of the third class, since no evidence of absorption is in 

 general shown in their spectra, beyond the appearance 

 of lines such as are seen in our sun. For the stars of 

 the second class, however, this view seems more reason- 

 able, since many of them exhibit spectra which are 

 strongly banded. 



"One great advantage of the study of the stars by 

 physical instruments, as the spectroscope and photometer, 

 is that some clew is given to certain laws, for our knowl- 

 edge of which we must otherwise depend on theoretical 

 considerations alone. While the conclusions to be 

 drawn from micrometric measurements are, in general, 

 much more precise, and the effects of the errors can be 

 more certainly computed, they fail entirely to aid us in 

 studying such laws as are here considered. For exam- 

 ple, the present investigation serves to study the follow- 

 ing important problem in cosmogony, to which micro- 

 metric measures contribute nothing, and which can 

 otherwise only be examined from the standpoint of 

 theory. 



If we admit a common origin to the stars of the Milky 

 Way, a general coincidence in their axes of rotation seems 

 not improbable, especially as such an approximate coin- 

 cidence occurs in the members of the solar system. If 

 the coincidence was exact, the direction must be that of 

 the poles of the Sun, or, approximately, that of the pole 

 of the ecliptic. On the other hand, since the stars of the 

 Milky Way are supposed to be arranged in the general 

 form of a flattened disc, we should more naturally expect 

 that the axes of rotation would be symmetrically situated 

 with regard to it, or would coincide with its shortest di- 

 mension. According to this theory, then, the axes of ro- 

 tation would be directed towards the poles of the Milky 

 Way. If now we suppose ihat a great number of vari- 

 able stars were distributed over the heavens, it is evident 

 that those seen in the direction of their axes would not 

 appear to vary, since, as they turned, they would always 

 present the same portions of their surfaces to the observer. 

 Those at right angles to this direction would show the 

 greatest variation, and, other things being equal, would 

 appear to be more numerous, since they would be more 

 likely to be detected. If then the axes are coincident, 

 we should expect that most of these variable stars would 

 lie along the arc of a great circle whose pole would 

 coincide with their axes of rotation." 



" Thirty-one stars are known whose period is less than 

 72 days. Of those, six belong to the fourth class, or that 

 of fiPersci, in which the variation is probably due to the 

 interposition of an opaque eclipsing satellite. Of the re- 

 mainder, seven may be excluded, since they are red, and 

 may belong to the second class, or that of o Ceti. 

 Eighteen remain, whose periods vary from less than a 

 day to 54 days, and which may be placed in the third 



class. All lie within 1 6° of a circle whose pole is in R. 

 A. I3h, Dec. + 20 . The distances of eleven are from 

 o° to 5 , of five at distances of 8° and 9 , one at 14° and 

 one at 16 . The average distance is 5.°5, while, if the 

 stars were distributed at random it should be 30 ." 



The dome erected by Sir Henry Bessemer for the re- 

 ception of his new and powerful telescope is now nearly 

 finished. The telescope itself has arrived from the mak- 

 ers, and is now ready to b£ set up. It has been construct- 

 ed on a plan devised by Sir Henry Bessemer, which it is 

 believed will permit of telescopes being made on a much 

 larger and more powerful scale than even the present one, 

 which is the largest in the world. The present instrument 

 is capable of being directed to any part of the heavens at 

 the option of the observer. The upper portion of the 

 dome is made of glass, with windows facing in every di- 

 rection, and within there will be placed mirrors of silvered 

 glass, which is part of the new invention, silvered glass 

 being used in place of metal. The room and dome with 

 its windows will revolve and keep pace automatically with 

 every motion of the telescope, and the upper end of the 

 instrument will reach a height of about forty-five feet. 



Washington, March 24. W. C. W. 



DISCREPANCY IN RECENT SCIENCE. 



There are two classes of statements in current scientific 

 literature that do not harmonize. Their teachings are op- 

 posite ; yet, the sayings are daily used by men who believe 

 both to be true. One series of doctrines is known as the 

 " Conservation of Energy ; " the other, the " Nebular Hy- 

 pothesis." The structure of nature rests on one, while the 

 history of cosmic evolution is based on the other. Then 

 they should agree. Men are fascinated with cosmogony, 

 and forages have sought the laws by which the Universe de- 

 veloped. This research culminated in the existing Nebular 

 Hypothesis. Other fields of study were opened, man scru- 

 tinized his environment, analyzed matter, searched for its 

 ruling laws and summed up results in the doctrine of the 

 Conservation of Force, Now the laws by which nature 

 was in the past evolved, and is in the present governed, 

 must be, and are the same. Such does not seem to be the 

 teaching of some late popular books on science. 



By a generalization of late research it is annnounced 

 that the Universe is a unit. All suns visible in the tele- 

 scope are composed of similar material, since they emit 

 light, having like properties, and are dominated by the same 

 laws of gravity and motion as rule the solar system. 



Like matter, like laws, is the postulate of nature for all 

 time. Some scientists ignore this apparent truth, as will 

 be seen in comparing ideas advanced in recent works. 



The fundamental axiom in the law of the interaction of 

 force is, that when one mode of energy appears, another 

 vanishes, and vice versa. 



No form of force can become sensible without the re- 

 tirement of another of equal intensity. This mutual dis- 

 placement never ceases for an instant, and the system of 

 nature is kept up by the How, interchange and conversion 

 of force. Conservation is the law of energy, and no one 

 force can long act without waning and giving rise to an- 

 other. Gravity, motion, electricity, magnetism, chemism, 

 heat and light, are forms in which energy exists ; yet one 

 never can work eternally by itself, but must suffer conversion 

 into another mode of power. Motion in molecules evolves 

 heat, and heat acting upon still molecules appears as mo- 

 tion. Chemism acts, gives rise to heat and in doing so 

 expires ; or it may exhaust its energy in conserving elec- 

 tricity, which in turn may develop into heat. Numberless 

 like instances might be given to prove the conservation of 

 energy, were they necessary, but they are not ; this great 

 law is universally accepted by students of nature through- 

 out the world, and the closest reasoner cannot find objec- 

 tion to this deduction of science. Among many facts re- 

 vealed by the discovery of the laws of force, one only is 



