June, igo6.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



449 



brilliant spwctriim by means of a Thorp replica grating-, 

 tbc ravs of anv portion of the spectrum becoming 

 in this way available for the illiiniin;ition of the object. 

 As the result, whereas the detailed structure of the diatom 

 was revealed wilh green light, this \\.is not the ea^.;- 

 with vellow light. 



From I'rof. J. Milne, h'.R.S., and I'rof. F. W. Ovson, 

 F.R.S., of the Royal Obscr\atory, Edinburgh, came 

 seismograph records of recent earthquakes, affording 

 sug'gcsti\e comparative material for the discussion of 

 seismograms relating to the h'ormosan, Columbian, 

 and San l>'r;inciscan earthquakes of this vear, as well 

 as (il lour disturbances occin'ring in 1905. Iwo 

 diagi.iTus <il the Columbian <'arlhr|unl«\ which 

 I'nif. Mihie showed, had been, il is ol interest to note. 

 n.M-ord:<l wilh a pi-ndulum, weighing in I he one case 

 80 lbs., with a pi'rio<l of 25 seconds, in the other the 

 weight was only ;i few ovmccs, with ;i period of 15 

 seconds. Both had n'corded the period for the large 

 waves as 17 .s.i'coiids. According to this observer, in 

 the 13 years' inter\al, i8gj-r904, there .are records for 

 ■at least 750 " world-shaking " earthquakes, which m.i\ 

 be referred to three periods continuous with each otliei', 

 and each two-tenths of a year or 7;^ days' duration. 



In n.alural science Ihe Marine liiologic.al .Vssociation 

 were responsible for a small collection of living fishes 

 from the shoi'e .and shallow w.ater. illustrating the 

 differences in habit .and mode of life adopted by different 

 species. On beh.ilf of I'rof. .\ntonio Rerlese, occupant 

 of the ch.iir ol /oology in Ihe Cnixcrsity of Naples, 

 Mr. Cei-il W'.arburton brought thi^ former's ingenious 



r/LLlUC Tuec 



ITCH JACKET 



F>/P£ rOR EMPTYING 



THE JACKET fS 



INOENTtO HERE 

 TO RECEI V£ BURN En 



BONSF.NS 

 BUfiNEH 



VESSEL WITH WATEH 

 FOB RECEI Vine CAPTURES 



.■rp|);ir.ilus lor <':ipluring minute inst-cls, the ,aclion ol 

 which is s-.'iMi in Ihe .iccompans ing section di.a- 

 grani. The hollow nu-t;il cone is boiiiidird l)\' a 



water jackc^t ; on the open base of the iiuerted cone 

 rests a lra\' madi- of \\ ire gauze, designed to carry moss 

 or any other materi;d which forms the natur.al harboiu"- 

 ing quarters of small in.sects. If the v.ater in the 

 jacket is maintained at a 1emper.il\ue of about 70" 

 Centigrade the tiny denizens prefer to quit tlu- moss, 

 but since no footing is obl.ain.able along the sloping 

 .'ides of the cone thev f.ill into the glass rec<-ptacle 

 placed at the apical end of the cone. From there they 

 can be transferred to a dis.secting microscope, if re- 

 quired, for idcntilication or examination. Mr. Stanlev 

 Ciardiner and Mr. 11. I'. Tliomasset's fine series of 

 enlarged photographs of the vegetation of the 

 Seychelles indicated Ihe sharply divisibU> character of 

 the llor.i due to soil characteristics. 



The Stellar Universe. 



F.. CoKK, |-.R..\.S., M.R.1..\. 



TiiA'r our visible imiverse is limited in extent there is 

 .abundant evidence to show. The number ol stars visi- 

 ble to the naked eve is not only comparatively small, 

 hut absolutely so; and the mmiber which will .appear on 

 the |ihotog-raphic charts of the sky, now in progress, 

 will probably not exceed 100 millions. .And even this 

 l.irge muiibir is comparatively sm.all. The richest man 

 in the world is said to possess as many sovereig'ns; and 

 in a ten-.acre field of ripe oats the number of grains of 

 ■ orn probrdilv exceeds the number of the visible stars.* 

 Taking the popidation of the earth at 1,500 millions, we 

 ha\e tin- rem.-irlsable f.aet that for e\erv star in the sky 

 there .ire 15 hum.-m beings living on our little globe. 



The mmiber of stars visible to the n:iked eye has been 

 \.iriouslv estimated. The photometric measures made 

 at Harvard Observatory show the following; figures : — 

 Lender magnitude 2, 38 stars; under 3.0, t^q; under 4.0, 

 317; under 5.0, 1,020; and under 6.0, 2,863; •'>tal 4,339 

 to the (ilh magnitiule. The coellieient of increase for 

 each m.ignilude is .about 3; th.il is, the tot:d number 

 down to any given magnitud<' is about 3 times the 

 mnnber of all stars brighter than that magnitude. Pro- 

 lessor Xewcomb thinks that there is no evidence of de- 

 crease in this coeHieienl down to the loth magfnitude. 

 Ihit a dimimition in the r.ate of increase must set in 

 'iimcwherc lielow the 10th m.'ignitude, for otherwise 

 tile numlit-r ol the xisilile stars would be considerably 

 greater than it ;ictiially is. T.aking the total number 

 of ^^tars to magnitude ().o as 4,339, and allowing a factor 

 of 3 for the total number to each magnitude below this, 

 1 lind that the total number down to the 15th magnitude 

 'lould be .about S3 millions, to the Idth magnitude 

 .about 23(1 millions, and to the i7lh magnitude — about 

 the fainti'-t \isiblein the great ^■erkes telescope — about 

 7()S millions. It is exitlenl, therefore, that there 

 must be a diminution, or " thinning' out," of the visible 

 stars :it some point in space. This diminution in the 

 increase probablv begins with stars of the loth or nth 

 magnitude. \ow what is the cause of this decrease in 

 number as the stars become fainter? Is it due to an 

 .actual decrease in number as we approach the limits of 

 the visible unixerse, or is it caused by an extinction of 

 light in the ether of space? The latter seems im- 

 prob.ible, Inr Professor Seeligcr finds that stars of the 

 I Ilh and 1 1 ', magnitude are comparatively few- in nimi- 

 liri 111:11 the poles of the .Milky Way, but are very 

 nunnrous in tlie C.il.ixy itself. This is al.so true for 

 f.iinler stars, such .is those seen by Sir William 

 llersehel in his "gages." Photographs give similar 

 results. Dr. Roberts' photograph of the Milky Way 

 in Cvgfiuis shows about 8,500 stars to the square degree, 

 w hile a photogTaph taken near the North Cialactic pole 

 shows only T78 stars to the square degree, the average 

 for the whole sky being about 2,300. It seems 

 riasonable, therefore, to conclude that if faint stars arc 

 .ipparentb few in number near the poles of the Milky 



'This I have foiimi hv .ictii.il e.sperimcnt o\\ llic niimlier of 

 grains on .1 squnro foot. 



