26 Frauenhofer o;i the Refractive and Dispersive Pozvers 
I had still another which hung out, and from this also I for- 
ced a cast, but by a method which has been often adopted by 
others. I carried the full hive into a dark place, turned it up, 
placed an empty hive over it, mouth to mouth, and drove it par- 
tially. Perceiving that half the bees had gone up, and know- 
ing that in these cases the g[ueen is always among the foremost, 
I immediately replaced the old hive in its former station, and 
carried the new one, containing the queen, to a little distance. 
As the old hive had plenty of eggs and young brood, the bees 
were at no loss to procure another queen ; and the new one ha- 
ving a queen, proceeded to work in all respects as a natural 
young swarm. The old one I kept over winter, and it cast this 
summer. 
Art. V. — On the Refractive and Dispersive Power of different 
Species of Glass, in reference to the improvement qf Achro- 
matic Telescopes, xvith an Account of the Lines or Streahs 
which C 7 ' 0 ss the Spectrum. By Joseph Frauenhofer of 
Munich. Concluded from Vol. IX. p. 299. 
As the lines of the spectrum are seen with every refracting 
substance of uniform density, I have employed this circumstance 
for determining the index of refraction of any substance for each 
coloured ray. This could be done with the greater exactness, 
as most of the lines are very distinct and well marked. For 
this purpose, I selected the largest lines, because with substances 
of low refractive power, or with prisms.of small refracting angles, 
the lines of less magnitude could scarcely be perceived with a 
strong magnifying power. The lines which I chose were those 
marked B, C, D, E, F, G, H, in Fig. 5. of Plate VII. (Vol. IX.) 
I made no use of the line h, because it is too near F, and I endea- 
voured to. use the middle one between D and F. It is not practi- 
cable to measure large arcs, such as BH, but only small ones like 
BC, CD, because, in order to see the lines of the different co- 
lours distinctly, the eye-glass requires to be displaced. 
The following Table contains the measures of the angles ob- 
tained from different kinds of glass, and other refracting sub- 
stances. 
