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Technical and Bibliographic Notes / Notes techniques et bibliographiques 
 
 Th« InstHut* hat atttmpltd to obtain th« bttt original 
 
 cow avaHable for filming. Features of this copy which 
 may be bibliographically unique, which may aRer any of 
 the images in tha reproduction, or which may 
 significantly changa the utual mtttwd of fflming ara 
 chedced below. 
 
 □ Coloured covers / 
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 □ Covers damaged / 
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 □ Covers restored and/or laminated / 
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 I Cover title missing /lje ttre de couveitwe manque 
 
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 Encre da couiaur (i.*. atiba qua blaue ou noira) 
 
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 □ Only edition available / 
 SeulaMMondiaponMa 
 
 □ light Unding may cause shadows or distortk>n along 
 Interior margin / La reikire serr^e peut causw da 
 rombre ou da la tfMnion la ioi^ da la marga 
 int^rieure. 
 
 □ Blank leaves added during restorations may appear 
 within the text. Whenever possible, these have been 
 omMadftom filming / Use peut que certaines pages 
 blanches ajout^es iors d'une restauration 
 spparaissent dans ie texte. mais. torsque cela itait 
 posaiMa. eat pagaa pas M fftniaa. 
 
 Additional comments/ Peginetlon ia 
 
 CommamalraasuppMmanlaiias: pagination 
 
 L'instRut a mierofUmi Ie meilleur exemplaire qu'il lui a 
 M possibia de se procurer. Les details da cat exem- 
 plaire qui soni peut-«tre unk)ues du point da vua bibR- 
 ographkpe. qui peuvent nwdKler une image reproduile. 
 ou qui peuvent exiger une modificatkm dans la mllho- 
 de normale de filmage sont indk)u<s ci-dessous. 
 
 I [ Coloured pagas/Pagas da couiaur 
 
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 Con^and du materiel si^^mentaire 
 
 □ Pages wholly or partially obscured by errata slips, 
 tissues, etc., have been refilmed to ensure the best 
 possible Image / Les pages totatamant ou 
 partiellement obscurcies par un feuillet d'errata, une 
 pehire, etc.. ont M film^es k nouveau de fa(on k 
 obtenir la maiaura image posiribla. 
 
 □ Opposing pages with varying colouration or 
 dIseoiouratkNW ara flbned iwfea 10 antura ttw batt 
 possible image / Les pages s'opposant ayant des 
 colorations variables ou des d^cotoratlons sont 
 likn<as deux fois afin tfoManir la maMaura hnaga 
 
 follovs: p. 199-200. 
 coBM suit: p. 199-200. 
 
 tOx 
 
 14x 18x 22x 26x 30x 
 
 I I I I i I 1 I I I 1-/1 I I ITTl 
 
 Ifx 20x 24x aix 
 
 12s 
 
 92x 
 
Th« copy filmed h«r« hM bMn raprwIiiMrf ttin l n 
 to th« flMMTOWty of: 
 
 University of Toronto 
 
 Gerstein Sciences Information Centre 
 
 Th« imagM appMring hara ara tha bast quality 
 pesaibia conaMaring tha condition and lagibillty 
 of tho orltliiol eopv oftd in hoopi n g wMi tiw 
 
 Origifiol e o p loa In printod popor oovors aro Mmod 
 bag Inning wiiti tfia front oow and anding on 
 tha last paga with a printod or Hluatratod Impraa 
 •ion. or tha back eovor whan approprlata. All 
 othar original copiaa ara fllmad boginning on tha 
 first paga with a printad or Hluatratod Imprao- 
 alon. and onding on tho loot pofo wMi o printod 
 or WiMtfscod improoalont 
 
 Tho laat racordad frama on aach microflcho 
 shall contain tha symbol (mooning "CON- 
 TINUED"!, or tho symbol ▼ (mooning "iNO"). 
 whiolMvor oppMoOa 
 
 IMopo. platao. charts, ate., moy bo fiimod ot 
 diffarom raduetien ratios. Thoaa too iorgo to ba 
 antiraiy includad in ona axposura ara fllmad 
 beginning in tha uppar laft hand eomor, loft to 
 right and top to bonom, as many frames as 
 raquirad. Tha following diagrams iUuatrata tho 
 inotliods 
 
L'M«mplair« film* fut w p r od yh sriM A to 
 
 University of Toronto 
 
 Gerstein Sciences Information Centre 
 
 Lm imagM suivantM ont *t* reproduitM avac la 
 plus grand soin. compta tanu da la condition at 
 da to nattat* da raaampto^ film*, at an 
 
 Ua aiiamptolraa ariginaua dont to aoiraartwra an 
 papiar aat iniprinida aont fHmda an eomman^ant 
 par to pramiar ptot at an tarminant soit par la 
 darniira paga qui comporta una amprainta 
 d'impraasion ou d'llluatratiMi. soit par la sacond 
 ptot. aaton to eas. Toua toa awtraa aaamptoiraa 
 O fl g inaui i sont fHmda an eowwianyant par to 
 pfaniMva paga quI aonipwta tma ampraints 
 d'impraasion ou d'illustration at an tarm inpm par 
 to damtora paga qui eomparta una taito 
 
 Un daa symbolas suivants apparaitra sur la 
 damiira imaga da ehaqua micrefieha. salon la 
 eaa: to aymboto signifto "A tUIVRI". to 
 vynNMia ▼ atgnma rf iv • 
 
 Laa canaa. ptonchaa. tabtoaux. ate., pauvant *tra 
 fltomte A rfaa tMiM da rMuatton dtftArants 
 Lorsqua to documant ast trap grand pour itra 
 raproduit an un saul cliche, il ast film* A partir 
 da i'angto supAriaur gaucha, da gaucha i droita. 
 •t da haut an baa. an pranant to nombra 
 tflmataa nteaaatira. Laa dto y p mm aa anivbnta 
 
 1 
 
 2 
 
 3 
 
 3 
 
 6 
 
J) 
 
 Rrprtnted (or privutc < in nl,itii>n irom 
 The AsT«OMiV!»K'Al Joi-BNAt, \ XI. MI, Ni>. s. M'"' 
 
 1-0 
 
 DESIR.\BILITY OF OBSERVATIONS OF THE SOLAR 
 ROTATION AT THE I IMI S OF ECI.IPSK 
 
 Tn th'' lini'-^ <>l' --pt'itrii from the solar limi) tluTc lilt iiilini; of 
 such nature as to alft'it the mcusurfments of tht- velocity of tlio 
 sun's rotation from the displacements of these h'nes. The mapni- 
 tude of till- olTi'it varies from line to line, \ arious fa(tor> eon- 
 tribute to the blendinR oi spectra." The factors oiu ratinj; l)etween 
 the moon and the point of ohser\-ation arc nearl\ eliminated just 
 before and after totality, when only the limb under observation 
 is visible. To inv( stijiate the problem a i)o\verful sju'i troseope 
 (proilucinj; .spectra of scale alK)Ut i mm to i .\) is necessary an<l 
 a large image of the sun preferred. The region of the ft-group is 
 su^>;este(l because the effect of liKmlini; is known for the /' lines 
 and others near them, and because iodine and chlorine conii>ari>on 
 spectra are available. It is ver>' desirable that such observations 
 be made at the eclipse of June S, so that terrestrial souri tsof lilended 
 spi'ctra may be removed in order to investigate the s»>lar and inter- 
 planetary sources. The observations need not interfere with those 
 during the precious seconds of totality. 
 
 At least one ])art\- is ])lanninj;' to make ileterminat ions of tlic 
 speed of rotation of the corona from displacements of the coronal 
 lines at the time of total eclipse on June 8. In view of the fact 
 that Deslandres. ("ami)bell. and Bosler haxc obtained \ahu- of 
 this speed of from ,^ to 4 km j>er second, it is very imjMjrtanl that 
 every precaution be taken to keep check on the errors that beset 
 such measurements, in this regard I would suggest that the si>ec- 
 troscope be used to determine the \ilocit\- of rotation of the 
 re\ersini; laver by observations of the last and west limbs of the 
 
 ■ Journal •■>' Ihr Royai .1 \lro>iomii ,tl Sm ni i lo, Joi 
 
 iqi6; Astrophysiittl Joiirmtl, 44, 177 -i.Sg, ami i<)<), n>i6. 
 •K<lwin B. Frost, Popular AslroHomy, a6, no, iqiS. 
 
 Ml), ^inil .t4i 45 7 1 
 
300 
 
 MFSOR COSTKIBl'TfOSS ASD NOTES 
 
 sun before and after totality of eclipse, using a comparison sjH-c- 
 trum and empioyinK precisely the same ntethoti in determining 
 the velocity from the coronal lines. In this way otu- can jud^c 
 as to the reliability of the latter. If it is im{K)ssihle to use an arc 
 or a spark comparison spectrum, the stronger iodine absorption 
 lines or the narrow strips of continuous spectrum between them 
 may be found suitable in the neighborhood of X 530^. 
 
 Ralph t. DeLiry 
 
 Dominion .\stbunomic.\l Ubservatory, Orr\w\ 
 April 1, 1918