136 Notices of Books. [January, 
lantern a wooden box about one foot in the side is recommended, 
furnished with various apertures capable of being closed by 
small sliding doors. Under the most favourable circumstances 
only about 12 per cent of the light emitted by the source can 
be made to fall on the screen. The author recommends the use 
of the screen as a blackboard ; and he gives a rather interesting 
account of objects for projection. Designs may be rapidly 
drawn on blackened glass, or on films of gelatine. Models may 
also be well shown by projection if care be taken to make them 
lie in one plane. The author remarks that it is an interesting 
experiment to projeCt the light itself upon the screen ; and if 
this be the sun, sun spots may be easily shown by the means. 
He further observes that by this means “ during a partial 
eclipse the phenomena may be watched by a large number at a 
time.” But, surely, in the latter case it would be absurd to 
watch an eclipse in this manner in a room, when it is possible 
to see the eclipse and the accompanying phenomena in the open 
air. Again, chromatropes, kaleidoscopes, and the growth of 
crystals are common objeCts for the lantern. The vertical 
lantern is a useful appliance for projecting on a screen such 
things as magnetic curves. A lantern galvanometer is also 
described. 
The final fifty pages of the book are devoted to Appendices ; 
the first of which relates to Electricity, while the second gives a 
most useful set of tables, of Squares, Cubes, Reciprocals, 
Powers, Logarithms, Natural Sines, Natural Tangents, Loga- 
rithmic Sines, Logarithmic Tangents, Constants, Properties of 
the Metals, Properties of Liquids and Gases, Hydrometer 
Tables, Temperatures, Pressure of Vapours, Wet and Dry Bulb, 
the Solar System, Double Stars, Clusters and Nebulas (with 
theirj Right Ascension and Declination). The constants are 
nearly all given in accordance with the metric system. Among 
the temperatures we find a cherry-red heat given as 900° C. 
(1650° F.), a yellow heat as 1200° C. (2200° F.), and a white heat 
as 1300° C. (2400° F.). It is much to be wished that new and 
accurate determinations of high temperatures were made by 
Siemens’s eledtrical pyrometer. 
The final Appendix contains some very useful hints regarding 
the cost and fitting up of a physical laboratory, which clearly 
prove that the cost of a physical laboratory ought not to much 
exceed that of a chemical laboratory, while the keeping up of it 
is certainly less, as there is a less consumption of material. A 
few pages (p. 296 et seq.) are well filled with a list of the most 
standard works of reference of each of the physical sciences ; 
also of tables, catalogues, and periodicals. Finally, we have a 
list of a hundred additional experiments, of which the following 
are examples : — 
“214. Measure the velocity of the bullet from a revolver, 
parlour rifle, crossbow, or catapult, with a ballistic pendulum. 
