LYMAN. 



THE SPECTRUM OF A CARBON COMPOUND. 



319 



Deslandres has analysed his Fourth Group into five series, character- 

 ized by sinall and not very regular second differences. The writer has 



TABLE II. 



Fourth Group. 



Deslandres. 



First Differences. 



Series 



IV 



482 

 480 

 490 

 512 

 521 

 523 

 536 



472 

 477 

 505 

 520 

 530 

 527 

 546 

 557 



Lyman. 



First Differences. 



VI VII VIII IX X XI 



474 

 501 

 513 

 533 

 539 

 549 



534 

 541 

 547 

 555 



556 

 567 

 576 



5S4 

 589 

 605 

 607 

 614 

 631 



633 

 652 



666 

 673 



been able to follow the arrangement into the region between A 2000 and 

 A. 1600 and has added seven new series of the same type. Table I. 



