1892.] Spectra of the Flames of Metallic Compounds. 121 



to the base of the flame, they cannot be ascribed to any of the final 

 products of the combustion, such as nickel oxide, but must be due 

 either to the as yet unaltered molecules of nickel carboiiyl, or to some 

 molecules intermediate between that compound and the products of 

 combustion which have only a transitory existence, and may perhaps 

 have a transitory agitation of a particular kind imparted to them by 

 the chemical energy which changes its form in the combustion. 



The following tables give the approximate oscillation frequencies 

 of the edges of the principal shaded bands, and of the lines seen at 

 the base of the flame, but the numbers are only approximate. 



Oscillation Frequencies of Edges of Shaded Bands. 



1496 1692 1933 2146 

 1521 1752 1960 2172 



1577 1808 2052 2199 

 1594 1849 2107 2226 

 1635 



Oscillation Frequencies of Lines in the Base of the Flame. 



1497 1582 1622 1721 

 1506 group of very 1627 I 1727 I 

 1509 closely set lines 1631 I 1732 Z 

 1514 1586 1651 1735 

 1518 1593 1656 1738 

 1521 1595 1663 1741 I 

 1526 1596 1667 1742 

 1543 1598 1671 1745 

 1547 1599 1673 1746 

 1549 1600 1682 1747 

 1555 1602 1686 1753 

 1560 1604 1690 Z 1806 

 1563 1607 1706 1809 

 1572 1612 1712 1827 

 1575 1615 1714 1833 



1578 1616 1716 1879 

 1580 1618 



The six numbers in the above table to which an I is added corre- 

 spond to lines which extend into the upper part of the flame. 



