the utmost conceivable delicacy. The principle of its construction is that the conducting power of metals is diminished by raising their temperature. Thus, if heat be applied to one only of the wires forming a circuit in which a galvanometer is included, the movement of the needle instantly betrays the disturbance of the electrical equilibrium. The conducting wires or “balance arms” of the bolometer are platinum strips 1/120th of an inch wide and 1/25000 of an inch thick, constituting metallic 18
Defined by the tint of the second hydrogen-line, the bright reversal of Fraunhofer’s F. The sun would also seem – adopting a medium estimate – three or four times as brilliant as he now does.
19
Annales de Chimie et de Physique, t. x. p. 360.
20
S. P. Langley, “Nature,” vol. xxvi. p. 316.
21
Sir J. Herschel’s estimate of the “temperature of space” was 239°F.; Pouillet’s 224°F. below zero. Both are almost certainly much too high. See Taylor, “Bull. Phil. Soc. Washington,” vol. ii. p. 73; and Croll, “Nature,” vol. xxi, p. 521.
22
This is true only of the “normal spectrum,” formed by reflection from a “grating” on the principle of interference. In the spectrum produced by refraction, the red rays are
23
Am. Jour. of Science, vol. xx. p. 36.
24
Am. Jour. of Science, vol. xx. p. 41.
25
Report of the Paris Observatory, “Astronomical Register,” Oct. 1883; and “Observatory,” No. 75.
26
Hipp. ad Phaenomena, lib. i. cap. xiv.
27
Cosmos, vol. iii. p. 272
28
Am. Jour. of Science, vol. xx. p. 437.
29
Nature, vol. xxiii. p. 19.
30
An expression used by Mr. Warren de la Rue.
31
Optice, p. 107 (2nd ed. 1719.) “Author’s Monitio” dated July 16, 1717.
32
“Der grosse Mann, der edle Pedagog, Der, sich zum Ruhm, ein Heldenvolk erzogen.”
33
“Zwar sind sie an das Beste nicht gewöhnt, Allein sie haben schrecklich viel gelesen.”
34
“Zwanzig Jahre liess sich gehn
Und genoss was mir beschieden;
Eine Reihe völlig schön
Wie die Zeit der Barmeciden.”
–
35
“Sicherlich es muss das Beste Irgendwo zu finden sein.”
36
“Dass die Welt, wie sie auch kreise,
Liebevoll und dankbar sei.”
37
“Will ich in Kunst und Wissenschaft,
Wie immer, protestiren.”
38
“An diese Religion halten wir fest, aber auf eine eigene Weise.”
39
“Was kann der Mensch im Leben mehr gewinnen,
Als dass ihm Gott-Natur sich offenbare?”
40
“Von der Société St. Simonien bitte Dich fern zu halten;” so he writes to Carlyle.
