VARIETIES. 
383 
Iodine. — An account has been published by M. Chatin of a series of ex- 
periments on animal and vegetable substances, with a view to ascertain the 
amount of Iodine that enters into their composition. All vegetables ap- 
pear to contain more or less of this element, and particularly water-cresses. 
Wine is much more rich in iodine than water, milk richer in the element 
than wine, and asses' milk more rich in this respect that of cows. Eggs 
contain a large portion of iodine. A hen's egg weighing an ounce and a 
half, was found to contain as much iodine as a quart of milk from the 
cow. Ibid, from Galignani. 
On the copying Electric Telegraph. By C. F. Bakewell. — In the method 
adopted for transmitting copies of writing, the letters to be transmitted are 
written on tin-foil with varnish, so as to present a conducting and non- 
conducting surface. The foil is placed on the cylinder of the transmit- 
ting instrument, and a metal style in connection with a voltaic battery 
presses on the surface of the cylinder as it revolves. By this means the 
electric current is continually broken when the style is resting on the var- 
nish, and as the style is made to tran verse by an endless screw from one 
end of the cylinder to the other, it passes necessarily over all the lines of 
the writing, and about eight times over each line. The receiving instru- 
ment is similar to the transmitting one, and on the cylinder of that instru- 
ment paper moistened with a solution of prussiate of potass in diluted mu- 
riatic acid is placed ; the metal style on that instrument being a piece of 
steel wire. When the electric current from the positive pole of the voltaic 
battery passes through the steel point to the paper, a blue mark is made by 
the production of Prussian blue, — and when the cylinder is in motion, the 
effect is to draw a series of spiral lines on the paper; but as the lines are 
broken whenever the varnish writing on the transmitting cylinder inter- 
poses, the forms of the letters are transferred from one instrument to the 
other — the writing appearing of a pale color on aground of blue lines drawn 
closely together. To produce this effect, it is requisite that both instru- 
ments should rotate exactly together, and this synchronous movement is 
attained by means of an electro-magnet — one instrument being made to 
regulate the other by retarding its motion at regular intervals. The regu- 
lation of the instrument is also greatly facilitated by a guide-line consist- 
ing of a strip of paper placed at right angles to the writing, by which, 
means the person having charge of the receiving instrument can 
ascertain exactly how much the speeds of the two instruments differ, and 
by the addition or abstraction of weight can bring the gaps formed by the 
strip of paper to fall directly under each other — which indicates that the 
two cylinders are revolving at the same rate. It was stated, in answer to 
questions by members present, that two hundred letters per minute might 
be copied by the instruments exhibited, and that five hundred in a minute 
are attainable. To illustrate the facility which this means of telegraphic 
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