joined cut, A
being a camera supported at an inclination of 56 degrees with the horizon,
and B the spherical flask silvered inside, while at D is placed the
ferro-prussiate paper destined to receive the solar impression. The dotted
line, C, may represent the direction of the central solar ray at one
particular time, and it is easy to see how the sunlight reflected from the
flask always passes through the lens. As the sun moves (apparently) in a
circle round the flask, the image formed by the lens moves round on the
sensitive paper, forming an arc of a circle.

Although it is obvious that any sensitive surface might be used in the
McLeod sunshine recorder, the inventor prefers at present to use the
ordinary ferro-prussiate paper as employed by engineers for copying
tracings, as this paper can be kept for a considerable length of time
without change, and the blue image is fixed by mere washing in water;
another advantage is the circumstance that a scale or set of datum lines
can be readily printed on the paper from an engraved block, and if the
printed papers be made to register properly in the camera, the records
obtained will show at a glance the time at which sunshine commenced and
ceased.

Instead of specially silvering a flask inside, it will be found convenient
to make use of one of the silvered globes which are sold as Christmas tree
ornaments.

The sensitive fluid for preparing the ferro-prussiate paper is made as
follows: One part by weight of ferricyanide of potassium (red prussiate) is
dissolved in eight parts of water, and one part of ammonia-citrate of iron
is added. This last addition must be made in the dark-room. A smooth-faced
paper is now floated on the liquid and allowed to dry.--_Photo. News._

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BREAKING OF A WATER MAIN.

In Boston, Mass., recently, at a point where two iron bridges, with stone
abutments, are being built over the Boston and Albany Railroad tracks at
Brookline Avenue, the main water pipe, which partially supplies the city
with water, had to be raised, and while in that position a large stone
which was being raised slipped upon the pipe and broke it. Immediately a
stream of water fifteen feet high spurted out. Before the water could be
shut off it had made a breach thirty feet long in the main line of track,
so that the entire four tracks, sleepers, and roadbed at that point were
washed completely away.

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