Broadstone, Dorset
June 10th. 1903
My dear Will1
Please look over the enclosed notes of experiments to determine the amount of power & heat, light &c.. in Star-light. The first paper is headed -
"The Electrical Measurement of Starlight"— (pp. 1.2. of notes) by Prof. G. H. Minchin2 & the late Prof. Fitzgerald3 of Trin[ity]. Coll. Dublin.
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I give you the substance of the paper, using the terms they use. Can you give me any idea of what the voltage 0.02, of Arcturus, acting constantly — day & night could possibly do, electrically or chemically — or take 1000 similar stars (about = whole of starlight) giving a voltage of 20.0
Look at p. 1 and 2 first. Then on p. 3. I give some American [2] results for heat only, — so enormously less. Can both be correct?
Also, is the E. M. F. of a candle supposed to be proportional to the light, or the heat, or the total radiation.
Please reply to this as soon as you can, as I am giving the facts in the last chapter of my book which I have now got to, & I want to finish it as soon as possible, as it has to be type-written & corrected & sent off by first week in July. I4 want to be able to show what these facts mean. — & what the total effect of Star radiation on earth may, possibly do. give me some suggestions.
Could you, next week, read over my type written copies of [3] some of my chapters, for errors in mathematics, chemistry, physics, &c. — or have you any friend at Newcastle up in such subjects, who would help you with difficult points; — also in general physiology — of plants especially — which I have had to refer to in one chapter. Also as to the general strength of the argument, I shall feel more comfortable if some one will read it over before I send it to the printers, as I want it to be so complete as hardly [4] to want any proof-correcting except for verbal errors &c. & then I need have only one proof-correcting which will save some time & labour. Please5 return me the Notes with your observations & suggestions. I have not seen "Wisdom on the Hare System."
Nothing is settled about the land yet, but they are going to make the new road first. I suppose Ma6 wrote you yesterday about Violet’s7 proposal. I am quite in favour of it, as this large house is wasted on us two, & I am sure she will soon get several day-pupils as there are lots of babies & little kids about.
We have had horrid cold dry winds the last 2 weeks.
The8 blue bells flowered in the wood very well.
Your affect[ionate]. Pa | Alfred R. Wallace [signature]
[2 words illeg.] Photos — poor.
Status: Draft transcription [Letter (WCP74.74)]
For more information about the transcriptions and metadata, see https://wallaceletters.myspecies.info/content/epsilon
1) Experiments on Light of Stars (-1895 with a Seleno-aluminium Cell, — sensitive to all rays from beyond red to beyond-violet — on an Electrometer measuring the Electromotive forces generated by the light of the different stars: — by G.M. Minchin1 & Prof. Fitzgerald2.
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A 2 ft. Reflecting telescope condensed the light on to the cell.
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A Leclanché cell produced on the scale a deflection of 530 mm. the slice being about 7 feet from Electrometer.
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Electromotive force due to Regulus equal to 4.25/ 530 — of a Leclanche Cell
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Do. do — … Arcturus = 7.5/530" "Arcturus produced a voltage of about 0.02."
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[2]2) Better observations another night gave (1895)
Arcturus ———————- 8.2 mm.
Vega —————————- 11.5 "
Candle at 9 ft. 10.0 "
Leclanché cell 513.0 "
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Observations in Jan.1896. with improved instruments. Electrometer gave deflection of 630 mm. on scale 7 ft. distant from mirror for one Leclanché call, or say 432 mm. for 1 volt.
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| Deflexn mm. | value in CandleLight | |
| Candle at 10 ft.—————— | 18.7 | |
| Beltegeuse (O Orionis)— | 12.80 | 0.685 |
| ϵ Orionis —————————— | 3.29 | 0.175 |
| Aldebarar ————————— | 5.21 | 0.279 |
| Procyon —————————— | 4.87 | 0.261 |
| α Cygni ——————————- | 4.90 | 0.262 |
| Pole star —————————— | 3.10 | 0.166 |
Note. Last col. gives ratio of E. M. F. produced by light of star in focus of 2 ft. diam. telescope to the E.M. F. of a stand[ar]d. candle light falling directly on the cell from distance of 10 feet.
[3]3) Some American experiments at the Yerkes Observatory (in 1900-1) gave the heat from Vega as equal to the 200 millionth of that from a candle at 1 metre distance. The heat form Arcturus being about 2.2 times as much.
Compare this with those opposite where Arcturus gives more less E.M.F. than Vega;— and the latter more than that of a candle at 9 ft. — say one third of a candle at 1 metre as compared with one 200 millionth of the heat!
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The American experiments were made with an a Radiometer of special construction for the purpose.
Status: Draft transcription [Enclosure (WCP74.8350)]
For more information about the transcriptions and metadata, see https://wallaceletters.myspecies.info/content/epsilon
Please cite as “WCP74,” in Beccaloni, G. W. (ed.), Ɛpsilon: The Alfred Russel Wallace Collection accessed on 10 May 2024, https://epsilon.ac.uk/view/wallace/letters/WCP74