Report of the Eclipse Expedition to Caroline Island, May 1883. (1884) / Chapter Skim
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Observations of Solar Radiation During the Stay on Caroline Island
Observations of Solar Radiation During the Stay on Caroline Island
Pages 63-89
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From page 63... ...
The ordinary thermometers were exposed horizontally, each attached by a brass support to the corresponding thermometer of the conjugate pair, and situated a couple inches above it. The instruments thus placed were in a favorable position for the desired observations, which were nlade hourly or oftener upon every clear day during the stay upon Caroline Island, beginning with April 27.
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From page 64... ...
lilacU Biifllit No 7 U No 751 No 1157 No 1150 No 4 No 3 No 2 No 1 A M Sun jiist outcniiK clontl 7 00 94 3 85 7 Sj) iinkling , bulbs wut 8 00 81 2 78 G Sun cloiir 105 1 95 0 88 2 9 00 130 0 89 2 80 0 Sun behind clouds 10 00 110 1 90 1 Sun behind t h i n c i i sti cloudu 108 7 95 7 90 0 11 00 134 0 98 0 93 0 Do 12 00 144 C 115 7 42 4 54 8 r M 40 8 3-1 8 101 1 95 3 Sun clear 12 10 142 9 144 9 114 9 112 8 Do 146 3 115 7 113 8 41 3 34 9 105 5 '9fi 2 12 12 144 7 102 0 90 5 Do 12 15 144 9 14G 9 110 0 114 2 41 2 35 1 37 8 102 0 95 0 Sun bohiiul thin oir str clouds.
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From page 65... ...
112 4 112 1 45 6 38 2 101 0 94 0 Sun clear 11 143 5 145 1 114 b 113 8 45 6 33 7 105 a 96 7 Do 11 30 144 0 146 b 115 7 114 4 45 6 39 9 105 5 97 5 Do 11 45 144 0 147 3 lib 0 114 8 45 6 39 5 107 0 it7 8 Do 12 00 143 2 146 2 115.8 115 0 45 5 39 9 106 8 98 0 Do P M 143 7 147 0 110 2 115 3 45 5 39 8 107 7 98 0 Do 12.15 12 30 144 0 147 0 116 9 116 0 45 5 40 2 106 5 98 0 Do , 1 03 147 7 149 2 119 1 118 7 46 5 41 1 108 2 100 0 Sun clear Max readings after clouds 1 30 141 0 140 7 115 6 114 9 46 0 39 5 105 7 98 0 Sun clear 2 10 138 0 139 8 115 1 114 2 46 0 39 7 101 0 96 0 Do 2 30 135 5 140 5 114 4 113 5 46 0 39 7 101 8 Ob 5 Do 3 00 139 0 137 9 112 2 112 0 4b 0 39 2 102 0 95 5 Do 3 30 1.K 0 133 0 109 8 109 0 45 9 i8 3 99 2 94 0 Do Siimmaiy -- Tionbled by passing clouds t.hionghout the day, though gcnor.illy clear when reatlings were made MONDAY, APRIL 30 Conjugate thorniomoters V I O L M ' S bulbs Oidiii.ary tlicinioiiietci's Time Black Biiglit Remarks Black Gilt Black Bright No 742 No 751 No 1137.
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From page 66... ...
U j i to .! 00 p m all leadings .are unusually good WEDNESDAY, MAY 2 Conjugate thcrmoniotcrs V O I L I F ' S bulbs Ordiuarj Ihcimomoters Tune Black Bright Remarks Bl.icK Oilt Bright No 742 No 751 No 1137 No 11.16 No 4 No 3 No 2 No 1 A M 6 30 90 2 91 0 83 5 84 0 28 0 28 2 83 3 82 0 Snu behind thin clouds 7 00 110 8 111 2 93 8 93 0 32 9 10 8 87 2 84 0 Sun clear 7 40 122 6 121 0 98 2 99 0 38 0 34 9 <)
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From page 67... ...
i in and .iftoi 2 00 p in wcio iiitetlciod with by p.isbiiig cloudb Botwoou these timesrti,idingi> .lie ich.iblc No laduitiouobsoivatious woio uutdcMay 4 ou account of clouds SATURDAY, MAY 5 Conjugate thcrmomoteis V I O L L E ' S bulbs Ordinary thciniomclois Tune BKick Briglit Rciuaiks BKick Gilt Bl.ick Bright No 742 No 701 No 1137 No 1136 No 4 No 3 No 2 No 1 A M 3 30 129 2 120 3 105 5 101 2 56 4 33 4 92 2 88 0 Sun in haze 10 00 157 5 vl37 2 109 5 109 2 39 7 35 7 93 0 91 8 Sun deal 10 30 142 6 142 5 112 5 112 5 41 7 .57 2 99 8 93 2 Do 11 00 142 0 142 5 111 7 111 9 40 S 5b 5 100 8 95 7 Do 11 50 143 0 141 5 112 0 112 5 41 4 30 7 101 5 95 0 Do 12 00 143 0 144 0 112 0 115 0 41 1 50 5 102 5 95 0 Suu just out ot Lir t,ti clouds Summai i/ -- Sky cloudy iieaily .ill day, but the low loadiugt. made aio ieli.ibIo " S Mib H O 9
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From page 68... ...
1137 No 1136 A M U 45 125 2 98 6 35 1 31 8 94 0 37 5 Sun cleai, but jiis>t cineigcd fiom clouds 9 57 157 0 105 1 33 3 34 8 95 2 89 2 Sun cleu 10 55 131 0 104 3 37 1 54 4 94 0 88 3 Sun cle.ii, |
From page 69... ...
CURVES OF BLACK AND BRIGHT BULB THERMOMETERS DURING ECLIPSE Tike. PM moo 10.15 10 30 1045 1100 1115 11 30 1145 1300 IStS 11 •30 12' '45 100 TIS[ \~10S' of -100° Black bulb freely oxposort Bright Sopointo obsorvatioiiH of blade balb o \^80' " " " bnght ' ?
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From page 70... ...
0 110 5 40 0 3() 0 98 0 91 5 Do The detailed obbeivations show A\ith snlTicicnt completeness tlie ooiiditioiis uiidci winch they wcic made The best d.iys upon \^hich to undtit.ike ladiation obseivations are tliose winch aic pcifectly cloudless, and, if possible, only such should be selected But duimg the whole staj on Caioline Island there was no cloudless day, and conscquentlj none of tlie observations weic made undei the best circuinstaiices Ho\\evei, on hcveral d.ijs, there were inteivals of se\eial bonis when the sky wascleai, and lesults of some value can be obtained at such times Tlie clouds, moreover, which so continuously prevailed were'ot the cuniulns tjpe, and these have, at least approximately, the effect of a scieeii placed bcfoie the sun, concealing it foi the tune being, but allowing it to shine again with its foimcr power when they have passed The metcoiological iccord shows that clouds of other vaiiotios weie iiuelj observed, though a haze was noted at tunes Tlie conjugate thermometers weie very sensitive to a slight diminution in the sun's heat I t lequiied only a very thin cloud to reduce the leadings by many degices, and it was some minutes aftei the passage of a cloud before the instininents rose to their pioper teuipeiatuie again Prom fifteen minutes to lialf an hour sliould be allo\\cd after tlic tciiipoiary coiiceahneiit ot the sun bcfoio the leidiiigs may be considered reliable, and a longer time may bo uecessaiy lu the case of the VIOLLE bulbs, winch aic slowei in their action on account of the time required foi the bnlbs of the tlieimoineteis within the spheres to be aflected by changes in the terapeiatnie of then outci suilaces It we select fiom the obseivations those in which the sun wa§ cleai at the tune, and Iiad been foi at least fifteen minutes pic\iously, we shall hnd a sufhcient uumbei to wariant a more extended examination I t is possible to obtain from them an estimate of the bolai intensity by sc\oial metiiods, and to institute a compaiison between them I t is also possible to obtain a value of tlie solar constant I n the computation which follows the solai intensity is obtained bj tlie methods available foi the conjugate theimometers, VIOLLE'S bulbs, and black and bnght bulb tliciinom eteis, and a compaiison made of the results, and in addition a value ot the solai constant is determined from the obseivations with the conjugate thermometers
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From page 71... ...
i t i o n o t t h e t h e o i y o f these i n s t i n m e n t s has b e e n m a d e b y T r o f W I L L I A M F F B B E L , a n d is t o b e p u b l i s h e d i n T r o f e s b i o n a l P a p e i o f t h e U n i t e d ' S t a t e s S i g nal Sex v i c e N o XIII I t assumes t h e l a w of D U L O N O ind PETIT, a n d d c i i v e s f o i m n l a i fox d e d u r i n g t h e s o l a i i n t e n s i t i e s a n d also t h e s o l a i c o n s t a n t Tiixough the couitcsy ot t h e a n t h o i , t h e f o i m u l i b h a v e been f n i n i s h e d fox t h i s c o m p u t a t i o n i n a d v a n c e o f t h e n p n b l i e a t i o n Tlioy aie as follows " Let 0 = the temperature ot the black bnlb 0i = t h e t o m p e r a t u x e o f t h e b r i g h t b u l b 0' = t h e t e m p o r a t n i e o f t h e i n e l o s n i e (shade t e m p a p i n o x ) I = t h e i n t e i i s i t j o f solax x a d i a t i o n ( c a l o i i o s p e i m i n u t e o n s q u a i e c e n t i u i e t i e )
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From page 72... ...
They sliow that in tiie obseivations undci discussion c is not strictly a constant, but varies with the tune of day. This may bo true ot the particulai instinments used, or be due to some circumstance connected with the exposnic ot the instiuinciits in these obseivations, or it may be inherent m this method of meas niing solar ladiation.
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From page 73... ...
lo^etl, tbc computed vabics would have been diininisbcd by about O 0 5 , and tbe mean of tbe lesidnals would lia\o been nearly 0 Thcic still would lia^e remained, is w is e \ p c a c d , plus icsidual" foi the moining and e^cn^lg obsoirations. Hid minus lesiduils ioi thoso tiken nexi the middle ot the d i j Tbe nngnitndc ot the residuals, whih laiger thin was hoped foi, is not sufhcicnt to pre\eiit the use of the method, but it lendeis idMSible the (omputition of the solai intensities bj equation (1)
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From page 74... ...
CURVES OF BLACK AND BRIGHT BULB THERMOMETERS DURING ECLIPSE VBVKA Tihe ? M lO-OO 10.15 10 30 1045 1100 U 15 11 30 11'45 1200 1.\Zt5 1Z50 12 '45 IM tlA \~105' of -100° Black bulb freely 03q)
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From page 75... ...
SOLAJl E C L I P S E , MAY G, 1883 71 Computation of iolar t»ten6»fi«« -- Gontnined. APRIL 20 IiitciiBiliy ( I )
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From page 76... ...
1 15 59 4 43.5 29 4 15 9 30 0 1 495 1 487 + 0 01 1 49 1 30 59 4 4) 8 29 4 15 6 30 0 1 469 1 487 -- 0 02 1 48 2 00 57 6 43.4 29 4 14 2 28 2 1.325 1 388 -- 0 00 1.30 3 00 58 2 41 8 29.0 16 4 29 2 1 526 , 1.438 + 0 09, 1 48 3 15 56 9 40 9 29 0 16 0 27 9 1 474 1.367 + 0.11 1 42 I n the preceding table the sixth column contains the dilference between the readings of the black bulb in vacuo {d)
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From page 77... ...
A n approximate value is sufficient for determining the relative intensities, which is the aim of the present investigation. The following table contains the computation for the same dates and tunes at which the readings of the conjugate thermometers were reduced.
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From page 78... ...
74 M E M O I E S O F T H E N A T I O N A L A C A D E M Y OP S C I E N C E S . Computation of relative solar inte^mttes.
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From page 79... ...
MAY 2 Time. Black Gilt An.
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From page 80... ...
The absoiption constant a is, however, different. I n the computation, the results of which are given in the following table, the value « = ^ is adopted as representing the theoretical value of the radiating power of the bright bulb in terms of that of the black bulb • Computation of relative solar intensities.
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From page 81... ...
This is not due to the eftect of passing clouds, as m the former methods, for the thermometers reco\ er quickly their former condition after the clouds have passed, but to changes m the velocity of the wind. The method is confessedly approximate, since the least increase m the force of the w ind which blows on the bulbs, or the least decrease, changes the effect of convection and so produces discordancies in the observations.
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From page 82... ...
The relatively small value at 12.00 on May 1 seems to be due to accidental conditions. The following table contains the relative intensities bj the three methods: Comparison of relative intensities by the three methods.
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From page 83... ...
A M 10 30 0 90 0 86 0 93 11 00 0.98 0 88 0 69 11 30 0 98 0 89 1 03 12 00 0 98 0 90 0 97 P M 12 30 0 97 0 92 1 05 1 00 0 95 0 95 1 09 1 30 0 90 0 92 1 01 2 00 0 92 0 88 1 04 2 30 0 87 0 85 - 0 89 MAY 0 P M 1 15 0 85 0 69 0 72 1 SO 0 84 O.bO 0 79 2 00 0 77 0 64 0 74 3 00 0 84 0 65 0 70 3 15 0 81 0.57 0 06 The above table shows plainly the effect of temporary influences in modityiug the observed intensities, and also that the different instruments are differently affected bj the same influences. In order to eliminate the accidental peculiarities and obtain a more reliable comparison of the methods the following table has been computed.
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From page 84... ...
1. The method of the black and biight bulb thermometers freely exposed in the n r gives only an approximate determination of the solar intensity.
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From page 85... ...
Fig.
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From page 86... ...
The cuive coirespondmg to the intensities given by the conjugate thermometers represents the relative solar intensities as accurately as the observations permit for the period April 28 to May 3. I t is impossible to give any mathematical estimate of the uncertainty of the numerical values which would be obtained from this curve.
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From page 87... ...
In § 1 there have been given values of the solar intensities obtained from the readings of the conjugate thermometers. These, after the rejection of a few discordant observations, were used in the above formulse for deriving values of A and p.
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From page 88... ...
feOLAE E C L I P S E , M A Y 6, 1883. 83 T A B L E II. -- Comparison of computed and observed solar intensities.
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From page 89... ...
The lesulting values of the solar constant have been given m Table I , and show excellent agreement. Collecting them here, with the interval of time covered by the observations on each day, we have the following results: SOLAR CONSTANT.
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