656 



NATURE 



\_Qct. 17, 1878 



Draper. 

 Lines of photographic 

 chart or solar spec- 

 trum, with their 

 condition. 



Fe. 



>> 



free. 



3864-50^ free. 

 3882-308 „ 

 3907-902 „ 

 3912-253 „ 



391975^ .» 



3945-101 „ 



39.S4"6o3 ^^ 



3961-60* „ 



3973'4o2 .. 

 3982-75^ „ 



3995*50^ „ 

 4069-862 „ 



4072-103 „ 



4075-502 „ 



4084-70* „ 



4088 -oo^ ,, 



4093 -20^ „ 



4104-402 „ 

 41 1 1 -00? 

 4118-00^ 



412I -20^ 

 4133-003 



4I42-9C/ Fe. 

 4145-302 free. 

 4152-90^ „ 

 4i5S"6oi „ 

 4168-20^ S. 

 4184-90' free. 

 4189-901 C. 

 4254-30! free. 

 4274-80* CrCa. 

 4278-103 Pb. 

 4303-00° free. 

 4316-602 „ 

 4320-00* TiC. 

 4325-101" Fe. 

 4328- loi Bi. 

 4331-002 free. 

 4336-34* SCr. 

 4345-152 free. 



4348-202 „ 



4353'oo2 „ 

 4365 -oqI BrCe. 

 4369-10* CrFeAs. 

 4394-503 free. 

 4413-202 „ 



4417-85^ „ 

 4445-002 „ 

 4450-002 Mn. 

 4463-002 Ce, 

 4467 -30I Ce? 

 4483-80! Fe. 

 4572-io3 Be. 

 4577756 Ce. 

 4582-102 FeCe. 

 4589-30* free. 

 4595-403 „ 



4599-803 j Sb 

 4600-15* I g;f- 



4629-603 free. 

 4640-503 „ 

 4648-15* Cr. 

 4661-50* free. 

 4674-90! CSe? 

 4698-653 free. 

 4704-65! Ba. 



Draper. 



Lines of 



electric spark 



in oxygen. 



Plucker. 



Lines of 

 oxygen. 



3864-751 



3882-303 



3908-001 



3912-353 



3919-502 



3945- I03 



395470^ 



3961-602 



3973-5010 



3982-703 



3995 •50" 

 4069-5010 



4071-90IO 



4075-45''* 



4084 •8o» 



4087-80* 



4093-10* 



4104-506 



4III-I0* 



4ii8-2oio 



4121-20' 



4132-906 



4142-906 



4145-50^ 



4153-008 



4155-75' 

 4168-40* 

 4185-008 

 4190-001" 

 4254-503 

 4275-006 

 4278-106 

 4303-00* 

 4316-508 



4319-75^ 

 4325-206 

 4328-20* 

 4331-20* 

 4336-006 

 4345'20» 



4348 -30I" 



4553-108 



4365-208 



4369-20* 



4394-50'' 



4413-201" 



4418-0010 



4445-006 



4450-033 



4463-008 



4467-208 



4483-75' 

 4572-20I 



4577-55' 

 4582-101 

 4589-5010 

 4595 ■50'° 



4600*003 



4629-60* 



4640-20I0 



4648- 1 510 



4661-508 



4675-008 



4698-50I0 



4705-0010 



4069-003 

 4072-00? 



4085-00* 

 4086-002 

 4094-002 

 4104 002 



4117-002 



4126-006 

 4135-006 

 4147-002 



4158-00* 

 4171-002 



4190-00'' 



4327-002 



4334-03- 

 4341 -oo® 



f 4347-00!' 

 \4348-ool' 



4369-00* 



4414-008 

 4418-008 



4443-00* 



4450-00* 



4457-00* 



4468 -ooio 



4474-0010 



4593-006 



4600-006 



4639 -ooio 

 4640-0010 

 4649-008 

 4662-00'^ 



4675-007 



4698-00'' 

 4705 -oo'' 



HUGGINS. 



Lines of 

 oxygen. 



4069*003 

 4073-003 



4117-002 



414900- 



4183-00® 



Angstrom 



Lines of 

 spark in air 

 attributed 

 to oxygen. 



4347-00 

 4364-00* 



4414-00'' 

 4416-008 



4467-0310 



4588-006 

 4596-006 



4640-006 

 4648*008 



4662 -oo^ 

 4677 -oo^ 

 4699-00'' 

 4706-00'' 



4069-50 



(4071-65 

 ^073-65 

 4075*50 



4103*00 



4155*00 



4184-50 

 4189-60 



4345-80 

 4347-50 



4414-60 



4418-30 



4590-80 



4595-90 



4640*25 



4674-75 



4698-00 

 4706-50 



The table presents what may be called the oxygen region of 

 the spectrum, only a few oxygen lines lying outside of its limits. 

 As this also happens to be the region in which our photographic 



apparatus and chemicals were most sensitive, we are enabled to 

 present measurements of the majority of the lines of oxygen. 

 It will be noticed that though the oxygen lines of greater wave- 

 length than 4704-65 are wanting, on account of their lack of 

 photographic power, this loss is partly made up by the exten- 

 sion of the measurements into the ultra-violet region, where as 

 yet no exact measurements of oxygen lines have been made that 

 I am aware of. 



That there should be no error regarding the nature of the 

 chemical element producing the lines, every precaution was 

 taken to have the oxygen as pure as possible. Photographs of 

 the spark in oxygen, between points of the purest platinum that 

 I could procure, were also made. These were compared with 

 the measured photographs of the spark between an iron and a 

 platinum terminal, and provision was thus made for the detec- 

 tion of any error that might have arisen from impurity in the 

 iron used in the terminal. As these photographs of the spark 

 between platinum terminals in pure oxygen presented all the 

 lines given in the table, these lines may be regarded as true 

 oxygen lines. In addition to the oxygen lines given, the fol- 

 lowing feeble lines were observed, regarding the nature of which 

 I was not quite satisfied, as they did not pass entirely across the 

 spectrum, viz., 4490-30 — 4505-80—4525-50 — 4548-75. In the 

 space extending from 4254-30 to 4345-15, many of the oxygen 

 lines are assigned to wave-lengths occupied by other elements ; 

 for example, Cr, Ca, Sb, Ti, C, Bi. As other lines of these ele- 

 ments did not present themselves in the measured photographs, 

 and as, the lines in question were also found in the photographs 

 of the spark between platinum terminals, they are 'to be regarded 

 as true oxygen lines, although they are not given by other 

 authorities. In some of the instances in which elements in 

 addition to oxygen are assigned to a weak line in the solar 

 specti-um, it is very possible that such assignments are in error, 

 because of a lack of fractions in the determinations of the wave- 

 lengths of these additional elements. Apparent discrepancies 

 regarding wave-lengths in my determinations, and those of the 

 other authorities, are sometimes explained by the fact that a line 

 which is recorded as single in one case, is given as two lines 

 in the other. It is also worthy of remark that in almost every 

 instance in which a line is presented by one authority and 

 omitted by the others, it is to be found in the colvimn con- 

 taining the photographic determinations, and is an evidence of 

 the superiority of this method of recording the existence and 

 positions of spectnmi lines throughout the region over which it 

 can act. 



Examination of the table shows that the differences between 

 the wave-lengths obtained for the lines of the electric spectmm 

 in oxygen and the lines of the solar spectnim are very small. 

 Out of the sixty-five lines of the solar spectrum which are, as 

 we have seen, assignable to oxygen, in seventeen the coinci- 

 dences are absolute ; in four the difference is only five one-hun- 

 dredths of a wave-length ; in twenty-two, ten one -hundredths 

 of a wave-length ; in four, fifteen one-hundredths of a wave- 

 length ; in eleven, twenty-one one-hundredths of a wave-length, 

 and in the remainder the greatest difference is only thirty-five 

 one-hundredths of a wave-length, or about that which Angstrom 

 has made in different measurements of the same line in the solar 

 spectrum. 



The small figure attached as a power to each wave-length of 

 the electric and solar spectra in the table is a proximate ex- 

 pression of the photographic strength of that particular line in 

 each spectrum, and an examination of these upholds the state- 

 ment made in a preceding paragraph that the oxygen lines of 

 the solar spectrum are very weak when no other element fur- 

 nishes a line which falls on the same wave-length. Of course 

 photographic must not be compared with visual intensities, for 

 as the one diminishes in the less refrangible regions of the 

 prismatic spectrum the other increases. An example of coin- 

 cidence in the lines of different elements, and consequent incre- 

 ment in strength, occurs in the line 41 18, and probably in the 

 line 4303 also, though it is supposed to be free. 



In conclusion, I give a list of certain lines in Angstrom's 

 chart which have not as yet been assigned to any element, 

 together with the wave-lengths of the same lines in my solar 

 and electric spectra. From this table it will be seen that 

 Angstrom himself observed a number of lines, the relations of 

 which to elementary bodies no one has as yet demonstrated, 

 and which I believe represent the oxygen in the solar en- 

 velopes. 



