I. On a definite method of qualitative analysis of animal and vegetable colouring-matters by means of the spectrum microscope

My attention was first directed to this subject by reading a report of Professor Stokes’s very excellent lecture at the Royal Institution, Friday, March 4th, 1864. It immediately occurred to me that a spectroscope might be combined with a microscope, and employed to distinguish coloured minerals in thin sections of rocks and meteorites. I was soon led to examine many other coloured substances, and found that the instrument is ore useful in connexion with qualitative analysis, when only very small quantities of material can be obtained. At first I employed the imperfect apparatus described in my Paper in the ‘Quarterly Journal of Science’, not afterwards, along with Mr. Browning, I constructed that described in my Paper in the ‘Popular Science Review’. For general purposes I do at think this could be much improved; but for chemical testing it is much less fatiguing to use a binocular instrument. There were many difficulties to contend with, but at length I constructed one which appears to answer all the requirements of the case.