LIVERPOOL CHEMISTS’ ASSOCIATION. 
4G7 
scope of Mr. E. Swift, jun., which followed Mr. Crookes’ lecture. This instrument 
is on the principle of the colour-top of Mr. Gorham, but Mr. Swift, by his various 
adaptations, such as an arrangement of friction wheels and a special mode of illumina¬ 
tion, is enabled to exhibit its effects to a large audience, and has thus succeeded in 
giving it a scientific character for illustrating the theory of the production of colours. 
In this instrument the base disk, which is about two feet in diameter, is divided into 
sections, exhibiting the primary colours of the spectrum. It is fixed vertically on a 
central axis or spindle, which can be rapidly revolved by means of the friction-wheels 
and winch-handle ; the face of the disk being illuminated by lateral jets of gas and 
reflectors. On revolving the disk at a speed of about 7000 revolutions peri minute, 
Avhite light results; further, on placing dark cards, with various designs cut in them, on 
the spindle axis and .on the face of the disk, and then applying motion to the whole, 
intermitting occasionally that acquired by the pattern cards, the play of colour which, 
succeeds is of the most brilliant and varied order. The illustrations with this instru¬ 
ment were highly applauded. 
The President said that what he ventured to express at the beginning of the evening, 
relative to the pleasure and instruction derivable from the various subjects exhibited and ex 
plained, he felt sure was fully realized, and he could not vacate his position of chairman 
without expressing his thankfulness to those gentlemen who had so largely contributed to 
the success of their conversazione. He felt assured that the audience shared his sentiments 
in this respect, and therefore he desired that they would join with him in offering a 
cordial vote of thanks to those gentlemen, and especially to Dr. Edwards and Mr. 
Crookes, for their very valuable services in contributing to their entertainment and 
instruction. The proposition was received with hearty acclamations, and the company 
separated at half-past ten, evidently much pleased with their evening’s enjoyment. 
The eighth general meeting of the session was held at the Royal Institution, on Thurs¬ 
day evening, February 16th; the President, A. Redford, Esq., in the chair. Messrs. 
Walter Wilson and A. J. Stephens were elected members of the Association. The do¬ 
nation of 1 The Chemist and Druggist ’ was announced. 
Dr. Edwards made a few remarks in reference to the paper read by Mr. G. F. Browne 
at the last meeting “ On Chemical Method,” and subsequently described the means lately 
adopted by Dr. Hofmann for proving the composition synthetically and analytically of 
water, hydrochloric acid, ammonia, and carbide of hydrogen: the four principal types 
on which the modern system of notation was founded. 
The President announced that Mr. II. S. Evans, who was to have delivered the lec¬ 
ture of the evening, <£ On the Application of Photography to Microscopic Illustrations, 
with Projections of Microphotographs,” was unavoidably detained in London that day. 
He regretted this very much indeed ; however, as Dr. Edwards kindly volunteered to 
take up the subject, the expectations of the meeting would not be entirely disappointed. 
Dr. Edwards enlarged upon the advantages to several branches of natural science, of 
the progress and improvements that were effected in optical instruments, and spoke of 
the efforts which numerous experimenters had been making in the endeavour to attain 
the same goal as Dr. Maddoc had reached so successfully. 
Of the advantages to physiologists and microscopists generally, of the remarkable ac¬ 
curacy of the high powers—such as the 20th, 25th, even to the 50th, lately added—capa¬ 
ble of practical employment in microscopic researches, he could not say too much, since 
the parts brought to view so distinctly by those high powers were of the most remark¬ 
able nature, and they opened as it were a new field for study and research. 
A number <3f Dr. Maddoc’s microphotographs were then thrown on the screen by the 
oxycalcine lamp, and were very much admired, on account of their delicacy and sharp¬ 
ness of outline. Dr. Edwards and Mr. John Abrahams gave short descriptions of the 
organization or habits of the subjects as they remained on the screen. . 
At the conclusion of the exhibition, Mr. Weightman spoke of a simple means by 
which some objects might be easily photographed, such, for instance, as would lequne 
an object-glass of one to two inches focus; with lesser objects he thought that amateurs 
would not be very successful, as the slightest vibration confused the picture. The me¬ 
thod suggested was simply to remove the photographic lens from the camera, aud to 
place a simple object-glass in its stead; the prepared plate being placed at any come- 
