250 Mr. Louis Bell on the Absolute 



This final result of Angstrom is certainly entitled to con- 

 siderable respect, and seems to be subject only to those 

 corrections which may be due to irregularities in the gratings. 

 These were, however, so poor compared with the grating- of 

 today that such corrections would necessarily be of uncertain 

 magnitude. 



At all events it is quite sure that, of the wave-length deter- 

 minations made up to 1880, those of Peirce, and Angstrom 

 corrected by Thalcn, are by all odds the best. 01' the two 

 Peirce's is probably the better, by reason of better grating.- ; 

 but his work will be discussed in another part of this paper in 

 connexion with the very recent works of Miiller and Kempt' 

 and Kurlbaum, which merit more extended study than Mould 

 be in place at this point. 



A tolerably complete bibliography of the subject up to date 

 is annexed. Many of the papers arc of little except historical 

 value ; but they will at least exhibit the various methods 

 employed, and the growth of exact experimentation. 



1821. Fraunhofer. — Denksahr. d.Ahad.d. Win. zu Munchen, viii. Hefl ii. 

 p. 38. " Neue Modification des Liclites dureh gegenseitig 

 wirkung und Beugung der Strahlen, und Gesetze uerselben." 



1823. Fraunhofer. — Schumacher's Astronomiscfie Abhandlungen, ii. p. 4(i. 



1823. Fraunhofer.— Gilbert's Annalen, lxxiv. p. 337 . "Kurzer Bericht 

 von den Resultaten neuerer Versuche iiber die Gesetze des Lichtes, 

 und die Theorie derselben." 



1835. Schwerd. — Die Beugungserscheinungen. (Mannheim.) 



1849. Stokes.— Athenaeum, No. 1143; Inst. xvii. p. 368. "On the De- 

 termination of the Wave-length corresponding with any Point of 

 the Spectrum." 



1851. Nobert.— Proc. Roy. Soc. vi. p. 43 ; Phil. Mag. £4] i. p. 570. " De- 

 scription and Purpose of the Glass Plate which bears the Inncrip- 

 tion — Longitudo et celeritas undularum lucis cum in acre torn in 

 vitro." 



1851. Nobert. — Pogg. Ami. Ixxxv. p. 83. "Ueher eine Glasplatte mit 



Theilungen zur Bestiminung der Wellenlange uud relativen 

 Geschwindigkeit des Lichts in der Luft und im Glase." 



1852. Drobisch. — Pogg. Ann, lxxxviii. p. 519. "Ueher die Wellenlange 



und Oscillationszahlerj der farhigen Strahlen im Spectrum." 



1853. Esselbach.— Berlin MonaUber. p. 7">7. " Ueher die Measung der 



Wellenlange des ultravioletten Lichts.'' 



1856. Esselhach.— Pngg. Ann. xcviii. p. 513; Ann. do ('him. et de IJii/n. 

 [3] 50. p. 121. " Eine Wellenmessung im Spectrum jens 

 Violetts." 



1856. Eisenlohr.— rogg. Ann. xcviii. p. 353, xcix. p. 159; Ann, de dim. 

 et de Phy8. [8j xlix. p. 504. "Die hrechharsten oiler unsicht- 

 baren Lichtstranlen in Beugungspectrum und ihre Wellenlange." 



18G3. Midler. — Pogg. Ann. cxviii. p. 641. "Bestimmung der Wellen- 

 lange einiger hell r Spectrallinien. ' 



1863. Mascart. — C. 11. hi. p. 138. " DSterminatioD de longueur d'onde 



de la raie A." 



1864. Maacart.-T-C. 11. lviii. p. 1111. "Determination des longueurs 



d'onde des rayons lumineux et des rayona ultraviolets." 



