PROCEEDINGS OP THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
137 
all the impurities necessarily contained in it, and it had so 
completely taken the place of natural madder that the culti¬ 
vation of the latter had almost ceased,and the land formerly 
used for madder-growing had been thrown free for other 
purposes. Artificial alizarine, he reminded them, was not, 
like the aniline dyes, a substitute for natural madder, but 
it was identical with the colouring matter of madder. 
One of the most remarkable properties of the natural ali¬ 
zarine contained in madder was its power of forming an 
insoluble compound with a mordant. (Mr Pullar here took 
some cloth which had the alumina mordant printed upon it. 
The pattern was of course as yet invisible, but on boiling 
the pieces of cloth for a few minutes—one in a solution of 
madder, and the other in a solution of artificial alizarine 
—it was seen that the colouring matter combined with 
the mordant only in the places where it had been 
printed upon the cloth, thus forming the pattern. It 
was also observed that both natural madder and artificial 
alizarine had given identical shades). Madder, or nowa¬ 
days artificial alizarine, was perhaps the most important 
of their dye-stuffs. It was with artificial alizarine that all 
the familiar Turkey red dyed fabrics were produced. As 
they were aware Turkey red was a very fast colour, yet 
still it was not infallible. There were chemical agents 
which rapidly destroyed it—notably chlorine gas. (This 
was illustrated by Mr Pullar destroying the colour of a 
piece of Turkey red cloth by placing it in a jar of chlorine 
gas.) That same principle, Mr Pullar continued, was 
made use of in obtaining printed designs upon Turkey 
red cloth. As the printer could not very well use chlorine 
gas as such to print with, the manner in which he proceeded 
was this:—He printed upon the red cloth a pattern with 
tartaric acid. He then passed it through a solution of 
chloride of lime. Whenever the parts printed with acid 
came into contact with the solution, chlorine gas was at 
once evolved. The red was therefore destroyed just in 
the printed parts, and a white pattern was the result. If 
the salt of lead was mixed with the tartaric acid a white 
discharge was produced as above mentioned ; but on pass¬ 
ing the cloth through a solution of bichromate of potash 
the pattern became yellow, owing to the formation of 
chromate of lead. If a certain proportion of Prussian 
blue was mixed with tartaric acid and lead salt, and the 
cloth treated in the same way, a design in three colours— 
white, yellow, and green—was produced—the green being 
formed by the mixture of blue and yellow. Mr Pullar, 
by a series of experiments, showed designs of the foregoing, 
and concluded by showing a novel design, specially 
prepared for the occasion—the “Fair Maid of Perth”— 
in white, yellow, green, and black. 
Dr Andrew Wilson, F.L.S., who was to have given an 
address on the Challenger Expedition, illustrated with lime¬ 
light views, was unavoidably absent, but the views were 
exhibited instead by Mr Patrick Geddes, F.R.S.E., 
Assistant-Professor of Botany in the Edinburgh Botanic 
Gardens. 
Dr F. Buchanan White, F.L.S., explained lime-light 
exhibitions of the microscopic structure of animals and 
plants. 
The following exhibitions were on view throughout the 
buildings 
In the Working Boys’ and Girls’ Hall four tables were 
fitted up with microscopes, divided into various sections, 
consisting of:—Botany, presided over by Messrs James 
and Henry Coates; Invertebrates, presided over by Dr 
Trotter; Geology, with Polariscope, presided over by 
Messrs Mackie and Macqueen, Perth Academy, and 
Robertson, Paisley; Diatomacese, presided over by Mr S. 
Keith, Perth; Entomology, presided over by Mr Marshall, 
Stanley; Micro-Photos, presided over by Mr Magnus 
Jackson; Pathology, presided over by Dr Ferguson; 
and Physiology, presided over by Mr James Stewart. 
On other two tables were exhibited a varied collection of 
physical and electrical apparatus. On one half of the first 
table was displayed a collection of various electrical lamps, 
both arc and incandescent—one of the latter being 1-candle 
power, and lit by a common battery. These were ex¬ 
hibited by Mr Loring, Manager of the Northern Electric 
Light Company, Dundee. On the other half of the table 
was a collection of electro-motors, pumps, &e., and a 
machine for turning vacuum tubes, which showed the effect 
of electricity in vacua. On the second table was a varied 
collection of electrical and other apparatus, including a card 
with a series of tubes showing the process of the manufac¬ 
ture of thermometers. On another table was a large selec¬ 
tion of acoustical and mechanical apparatus, Leyden jars, 
electro-motors, &c., which was principally exhibited by 
Mr Campbell, George Street. 
Mr Stewart also exhibited sections of human teeth, the 
circulation of blood in a frog’s foot, and microscopic pond 
life from the North Inch Pond. 
In the Society’s Library was shown its collection of 
Perthshire insects and shells. 
In the Boys’ and Girls’ Hall was exhibited a reflecting 
telescope, sent for exhibition by the Rev. DrGraham, Errol. 
The instrument was sent for the purpose of showing how 
from the simplest and cheapest materials a telescope 
capable of high astronomical work might be constructed 
by a person of ordinary mechanical ingenuity. The whole 
