276 
PROCEEDINGS OF THE SOCIETY. 
The diffusive unit value of the combination used may be termed 
the penetrating value of the red ray, whilst the standard neutral tint 
units used may be termed the luminous intensity of the light itself. 
Should the light be a coloured one apart from this condition of the red 
ray, it can be measured by altering the absorptive glasses in the usual 
way. 
The fixing of a unit value to the dispersive medium is effected by 
matching each combination with the standard glasses by means of normal 
daylight of a given intensity. When a match is made under these 
conditions the vision is unable to differentiate between the two lights, 
hence it follows that so far as the vision can determine the two combina- 
tions are synonymous. But it must be borne in mind that such a 
diffusive scale is in unit accord with the absorptive scale only so long as 
the particular light by means of which it was graded is maintained.” 
Mr. Nelson said that the subject brought before them by Mr. 
Lovibond was one the history of which was far too long a story to go 
through on that occasion, but the wonderful results obtained by means 
of his tintometer were perfectly surprising to any one who had an 
opportunity of testing its capabilities. It was in fact equal to discovering 
differences down to millionths of a tint, and having had the pleasure of 
seeing and using it he soon found that there was a very decided difference 
in the colour sensation of his own eyes which until that time he had 
never suspected. It had done such marvels when applied to macroscopic 
purposes that he did not doubt it would do much also when applied to 
microscopic studies. 
The President said that the value and importance of the subject must 
have impressed all who had heard Mr. Lovibond’s description. It was 
so important indeed that he could only regret that it had not been brought 
before them in the form of a paper so that they might have heard fuller 
details and have had them open for discussion. Unfortunately the time 
they were able to devote to exhibits was much too short for the con- 
sideration of a subject of such great interest. 
Mr. Nelson, in the absence of Mr. Halford, exhibited Mr. G. S. 
Marryat’s form of mounting and dissecting stand, and read a short paper 
upon the subject in which the construction and uses of the apparatus 
were fully described (see p. 270). 
The President thought he should for his own use prefer a rather 
handier instrument, and one that he could get on every side of. The 
system of whipping on hairs to handles for mounting purposes was well 
known, but he usually fixed them simply with a sailor’s double-hitch knot 
which he found very good for the purpose and perfectly tight in use ; it 
was certainly also very much quicker than whipping. 
The thanks of the meeting were then unanimously voted to Messrs. 
Nelson, Lovibond, and Halford for their interesting exhibits. 
Mr. T. F. Smith read the following note “ On the use of Monochro- 
matic Yellow Light in Photomicrography ” : — “ The former part of Dr. 
