287 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. VIII. 
movement, but the difficulty of description, though by no means removed, is 
immeasurably lessened by the use of the mirror. And the same with this 
specimen of iridescent iron ore ; its colours, which vary to the unaided eye, 
remain unchanged when examined by the mirror, To simplify the description 
of iridescent objects, therefore, I would advocate the above method, and 
would describe the result of such examination by recording the colour 
observed by aid of the mirror, and prefixing the term “ iridescent” to express 
the changing properties of the colour. Bearing in mind the unvarying nature 
of these changes, a far clearer idea may be formed of the appearance of these 
objects than from any attempted description of what is admittedly mdescrib- 
able, Time and space are also economised by the omission of lengthy 
descriptions. The accuracy, and therefore the value, of any description of 
colour, is always enhanced by mapping its spectrum ; more especially is this 
true in the case of iridescent colours. This is easily done, and by applying 
such map to a spectral chart, the order of the colour, and therefore its tint, is 
apparent. In examining many objects, chiefly birds or insects, by means of 
the mirror as above described, apparent exceptions are repeatedly met with 
to the fact stated above that the colour is invariable in tint and disappears by 
inclination of the body. Such instances are no real exceptions, but are due to 
the reflecting plates being curved, or having pigmentary matter beneath them, 
or an opalescent medium above them. In this way some of the most extra- 
ordinary and beautiful colour effects, it seems possible to conceive, are produced. 
Some of them I hope to bring before your notice on a future occasion. 
In examining objects with the perforated mirror a single light is necessary. 
The sun is of course the best, and the electric light probably almost as good. 
I frequently employ the lime-light, but a good paraffin lamp may be used as a 
substitute. Ordinary gas is unsuitable. The light should be placed in front 
of the observer, its direct rays being prevented from falling on the objects by 
means of a book or partition of some kind resting on the table, and of such a 
height that the light can be seen above it. On placing the mirror to the eye 
the light may be reflected from the mirror on to the object, and the latter 
manipulated so as to reflect the ray back through the perforation in the mirror 
to the eye, The incidence is thus known to be normal, and the colour 
observed is the one to be recorded. 
NOTES ON THE HABITS OF SOME LIVING SCORPIONS. 
By R. I. Pocock, 
THE literature which treats of the habits of living scorpions is not volu- 
minous, but it labours under the disadvantages of being based largely upon 
undetermined species, and of being often of questionable trustworthiness 
with regard to the statements that are made, Even accounts that have been 
given of late years of the same species of scorpion differ widely as to facts 
