128 
Quantity of 
Thallium. 
(2) O-1 gr. 
Harttev—An Investigation of the Connexion between 
A continuous spectrum cut off at 3530. 
Lines \ 5351 and 3776, strong. 
3530 
3519 
\ 5301 and 3776, fairly strong. 
A pair fairly strong. 
(3) 0-01 gr. Lines only. The pair above 
are feeble. 
(4) 0:001 gr. 
(3530 
(3519 
(5) 0:0001 gr. 
(6) 0:00001 gr. 
Lines \ 5351 and 3776 are moderately strong. 
The pair 
appear very feeble. 
The line \ 5351 is very faint; \ 3776 is fairly strong. 
The sole line visible, \ 3776, is very faint. 
Here the ultimate line is at \ 3776, and the quantity necessary to produce it is 
+i7 of a milligramme of thallium. 
The more recent quantitative experiments given here in detail were carried 
out by my assistant, Mr. A. G. G. Leonard, a.r.c.sc.1., during the past three 
years. 
Summary of the Observations on the Alkaline Karth-Metal Spectra. 
The spectrum of the metal in 
Mecke 
the Bunsen or burner 
flame. 
The flame spectrum of cal- 
cium, as obtained from its com- 
pounds, with the Mecke, or Mecke 
blast-burner. 
The same compounds, heated 
in the oxyhydrogen blow-pipe 
flame. 
CaALcIUM. 
With large quantities, there are four intense 
bands, one intense line, and three very feeble. 
The lines are identical with those in the spark 
spectrum, AA 4226°9, 4586, 4455, and 4435. 
With small quantities of calcium there are 
bands only. 
Bands only are observed. 
With a large quantity of substance, the 
spectrum consists of seven very strong bands, 
one intense line, and four comparatively feeble 
lines. The five lines are identical with the 
strongest lines in the arc and spark spectra of 
the metal. 
