April, 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



83 



Roberts*, as follows : (i) " continuous variation, in- 

 dicating that the component stars are in contact," and 

 (2) two maxima and two minima, showing that the 

 components are both bright bodies. The variation of 

 P Lyra; is well known. It is not usually considered 

 as an Algol variable, but it now seems probable that 

 it should be included in that class. Myers finds that 

 j3 Lyrie probably consists of two ellipsoidal components 

 revolving nearly in contact, the mass of the larger 

 component being 21 times the mass of the sun, and 

 that of the smaller g| times the sun's mass. He thinks 

 that the mean density of the system " is comparable 

 with atmospheric density " — that is, that they are " in 

 a nebulous condition." If this conclusion is correct 

 their diameters must be enormous. Taking the density 

 of atmospheric air as 814 times less than that of water, 

 I find that the larger component would have a dia- 

 meter of about 25 millions of miles, and the smaller 

 about 19 millions. The parallax of ^ Lyra? has not 

 been ascertained, but supposing it to be about one- 

 hundredth of a second, the sun would be reduced to a 

 star of about the loth magnitude. The maximum 

 brightness of the star is about 3.5 magnitude. It would, 

 therefore, be — with the assumed parallax — 6^ magni- 

 tudes, or about 400 times brighter than the sun. 

 From the diameters found above, the combined sur- 

 faces of the two components would be 1,332 times the 

 sun's surface. Hence their surface luminosity would 

 be less than one-third of that of the sun. This would 

 agree with Homer Lane's law, by which a gaseous 

 body gains in heat as it consolidates, and f* Lyra is 

 probably in a very early stage of stellar evolution. If 

 the parallax is larger than assumed above, the surface 

 luminosity would be still less. 



Another remarkable star is the Southern Algol vari- 

 able, V Puppis (Lacaille 3105). Both components are 

 bright. The spectrum of the brighter component is, 

 according to Pickering, of the " Orion type," B i A, 

 and that of the fainter B 3 A. The period of light 

 variation is 1.454 day. The spectroscopic measures 

 show that the relative velocity is about 380 miles a 

 second. The combined mass of the system is, there- 

 fore, about 70 times the sun's mass. As the star is 

 variable in light, the plane of the orbit must necessarily 

 pass through the earth, and the accuracy of this re- 

 sult for the mass is, therefore, certain. This great 

 mass, and the star's magnitude — about 4.50, shows 

 that it must be at an enormous distance from the earth. 

 According to Dr. A. W. Roberts, the density of the 

 components cannot exceed 0.02 of the sun's density, 

 and he finds that they " revolve round one another in 

 actual contact." Assuming this density and a mass of 

 35 times the sun's mass for each component, I find that 

 the diameter of each would be about loi millions of 

 miles. Now, comparing it with Algol, of which the 

 diameter and mass are known, and assuming the same 

 surface luminosity, I find that the parallax of V Puppis 

 would be about o".ooi8, or a light journey of about 

 1,800 years. As it lies in or near the Milky Way, it 

 may possibly be one of the larger stars of the Galaxy. 

 The parallax found above would indicate that the star 

 is about 5,000 times brighter than our sun would be if 

 placed at the same distance. The star is thus a very 

 remarkable and interesting object. Its mass is very 

 large, its density is very small, and the intrinsic 

 luminosity of its surface is very high. Its distance 

 from the earth is very great. Its orbital revolution is 

 very rapid, and the variation of light is small and very 

 regular. It is, in fact, one of the most remarkable 

 objects in the heavens. 



'Monthly Notices, R. A. S., June, 1903. 



CORRESPONDENCE. 



Creation of Species. 



To THE Editors of " Knowledgf.." 

 Sirs, — Replying to Mr. Herbert Drake's letter in your March 

 number, the strong; hold which the "dogma of coiislancy of 

 species " had obtained amongst theologians of that period is 

 illustrated by the fact that Robert Chambers published 

 "Vestiges of the Natural History of Creaton" anonymously, 

 in order to avoid involving the firm with which he was con- 

 nected in theological controversy, and the storm which followed 

 Chas. Darwin's "Origin of Species" shows that this precaution 

 was justified. 



From the active part taken by Bishop Wilberforce and other 

 prominent Churchmen of the time in this controversy, it would 

 appear that the objections taken to the dogma can scarcely be 

 dismissed as "popular prejudice or superstition," as sug- 

 gested by Mr. Drake. There can be no doubt that the strong 

 belief in this dogma held by the majority of the members of the 

 churches, whether popular prejudice or not, delayed the advent 

 of the theory of evolution. 



One grave objection taken to the theory of evolution was 

 that it did not accord with the literal reading of the first 

 chapter of Genesis. This was also an important objection 

 raised in the heated discussion which followed the pubUcation 

 of " Essays and Reviews," in which discussion many of our 

 Bishops took a leading part. 



J. C. Shenstone. 



" Common " ats a. Scientific Ternn. 



The word "Common "is a useful one for ordinary use, but 

 as a scientific term it has many disadvantages. Not the least 

 of these is its ambiguity. We may say " the common snipe," 

 or " the snipe is common there," or " the snipe is common to 

 several countries," and use the word thus in three different 

 ways, and not be sure that we shall be perfectly understood in 

 any of them. I had always myself understood the expression 

 "the common snipe " to mean the snipe that is ordinarily 

 meant by the word snipe without qualification. But Mr. F. G. 

 Aflalo {" Knowledge " vol. 2, p. 52) takes it to meau the 

 " prevalent " species of that bird. 



With regard to the Latin equivalents, coininunisin either of 

 these senses simply is not Latin. It can only, in that language, 

 mean common to two or more places. While vulgaris means 

 " ordinary," " as used by uneducated people." 



In this latter sense, which is I think the one in the minds of 

 most people, one could well speak of " The Common Dodo," 

 so as to distinguish the Didus Incptus of Mauritius from the 

 less well-known Didine birds of Rodriguez and Reunion. Vet 

 Mr. Aflalo would deny its appropriateness to any species 

 which is growing extinct. 



Another objection to vulgaris is that it connotes the idea 

 of popular error ; it would be more appropriately used to 

 stigmatise an incorrect title, than as a scientific distinction. 



To introduce the term " common sense " in this connection 

 seems like making " confusion worse confounded." We are 

 given three derivations of the expression. First, a man's five 

 senses were supposed to be the five avenues of one common 

 organ, hence styled " the Common Sense." Next, there is the 

 meaning of " the ordinary judgment of mankind." And then 

 there is the philosophical definition, which makes it equivalent 

 to the first principles of belief which ordinary men accept. 

 None of these have anything to do with the Latin communis 

 sensus, or the feeling common to all men as to what is right 

 and proper. In actual use these various ideas are so 

 confused that one can rarely meet two people to whom the 

 word conveys the same meaning. I remember a scientist 

 telling me that his common sense told him that miracles do not 

 happen. I pointed out to him that whether that were an 

 argument for or against miracles depended on the meaning 

 attributed to " common sense." Once I heard, shortly after 

 one another, two preachers, one of whom denounced, and the 

 other pleaded for, the use of common sense in religion. They 

 both meant the same thing, but used the term in contrary 

 meanings ! We need to be well on our guard against such a 

 doubtful expression. 



Verwood, Wimborne, March 13. Herbert Drake. 



