NOTES AND QUERIES. gi 
the wants of the working microscopist as these “ Studies in 
Microscopical Science,” and we hope that the whole issue will 
be subscribed for early. 
NortH oF ENGLAND MicroscopicaL Socrety.—On Feb. 6th, 
in the Committee Room, Literary and Philosophical Society, 
Newcastle-on-Tyne, Mr. C. E. Stuart, B.Sc., read a paper on 
Crystals, their microscopical character and investigation. The 
basis of this paper was a series of one hundred sections of 
minerals of common occurrence in rocks, cut_in special relation 
to their crystallographic axes, so as to distinguish the different 
systems of crystalline symmetry. This series was lent by Prof. 
Lebour, who at the close of the paper pointed out the accuracy 
of the cutting of the sections, and their special interest to students 
of petrology and mineralogy. 
But Mr. Stuart, bearing in mind that his audience as a whole 
had but a minor interest in those studies, made the body of his 
paper bear chiefly on the general physical character of the sections 
under examination rather than on the theoretical speculations 
based on their peculiarities, and intended also that it should serve 
as a general introduction to the microscopic study of crystals. 
To this end he commented with definitions and descriptions of 
crystals, the crystallographic systems, and their characteristics. 
The essentials of a petrological microscope were then set forth. 
Lastly, the striking points of the sections on the table came under 
consideration, as surface, cleavage, twinning, enclosures, zonal 
accretion, and so forth. The significance of these phenomena 
were pointed out, specially interesting being the light thrown on 
the origin of crystals and of rocks by the nature of the enclosures 
—either dusty matter or other crystals, or glass, or liquid, or gases 
fluid under strong pressure—found in the former. In connection 
with the purely optical effects produced by crystals, polarisation 
had special attention, and a short explanation of the cause of the 
production of the white light, darkness or brilliant colours seen 
when certain sections were viewed between two Nicol’s prisms, 
brought the paper to an end. 
A most excellent set of micro-photographs, a number of models 
of crystal forms, and the necessary microscopes for exhibition of 
the sections, kindly lent by Prof. Lebour, served to further illustrate 
the subject treated. i 
PERCEPTION OF LIGHT AND COLOUR BY THE LOWEST ORGANISMS. 
—An extremely interesting paper on the above subject, as illus- 
trated by Navicula, Paramecium bursariaand Euglena viridis may 
be found in Pfliiger’s Arch. Physiol, xxix. (1882) pp. 387-400. 
