Ad. MEMORANDA. 
descending from the sublime to the ridiculous—of which 
these designs are susceptible—a baker is changed into a 
sweep: for every design has two phases of colour, one being 
what is technically termed “complementary” to the other, 
dependent upon the position of the analyser ; for if the grapes 
appear “ruby bright,” by rotating the analyser a quarter of 
a circle they change to green, or a group of blue flowers to 
the “sere and yellow leaf.’ But these chromatic displays 
are not confined to mineral structures; for vegetable bodies, 
such as fous les mois, one of the starches, shows a black cross, 
similar to that seen in cale-spar; and such substances as 
whalebone and rhinoceros-horn present the most gorgeous 
display of colour, the phenomena being dependent upon 
varying degrees of tension in the structure of those and 
similar bodies. 
To those who would wish to make themselves familiar with 
this interesting and important branch of physical science, 
we would recommend the works of Woodward and Pereira, 
both being treated in a popular style. 
But to return to Mr. Highley’s instrument, figured in the 
annexed woodeut. The various parts are mounted on what 
the inventor calls a “gout-board support;” the upright is 
fitted with an adjustable panel, that carries a bundle of glass 
plates on one side and the stage and power on the other; 
this allows of the entire arrangement being accurately “ cen- 
tred” with any lantern with which it may be employed; 
when adjusted, the panel is clamped by means of a milled- 
head screw. The “bundle” consists of such a number of 
thin glass plates as will give a bright reflected heam of polar- 
ized light, and is attached to the panel at the proper angle 
for producing such a beam. ‘The spring stage for carrying 
selenite designs, unannealed glasses, pressure and heating 
clamps, and the larger objects, is formed within a large tube 
attached to the front side of the panel; and to the front 
of this is screwed a spring jacket, within which slides the 
power and stage for the smaller crystals employed. To the 
front part of the base-board an adjustable rod is fixed that 
carries the analyser, which consists of a large prism, made 
expressly for the purpose of giving a large and pure field of 
colour, the absolute fieid attainable being, of course, dependent 
on the intensity of the source of light employed, as oil, oxy- 
calcium, oxy-hydrogen, or the electric. Provision is made 
for rotating both the smaller and larger ohjects, when neces- 
sary for the demonstration of certain phenomena. When 
selenite designs are shown on the screen, the crystal power 
is replaced with another of suitable construction. ‘T'o use 
