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POPULAR SCIENCE REVIEW. 
simple body, its density, cohesion, crystalline or amorphous state, &c., but 
that these variations are never as extensive as those which certain specific 
heats would offer if dll the elements followed “ Dulong and Petit’s ” law ; 
3rd, that the specific heat of an element is the same, whether it be in the 
free state or in combination. 
Motions of Camphor on the Surface of Water. — Mr. J ohn Liglitfoot con- 
tributed an article on this subject to the Chemical News of June 27th. 
There was nothing very original in the communication, and still less in the 
suggestion appended to it, that, owing to its peculiar properties, camphor 
might be used to distinguish fabrics dyed with certain colours from others 
prepared in a different manner. In the same journal (July 18) a letter 
appeared from Mr. Charles Tomlinson, whose researches on this subject 
are familiar to many. In this communication, several of Mr. Lightfoot’s 
assertions are ably refuted, and it is satisfactorily proved that as early as 
the year 1748 the motions of camphor on water had been observed by 
Romeiu. 
An Improved Spectroscope — Analysis of the Fixed LineD. — The following 
extract of a letter from Professor Cooke has been published in a late 
number of the Chemical News . The writer having described the instru- 
ment, which has nine bisulphide of carbon prisms, by which the light is 
bent through almost 3G0°, states that he has arrived at these three results : 
— 1st. “ That the lines of the solar spectrum are as innumerable as the 
stars of heaven,” he having detected with this instrument <e at least ten times 
as many lines as are given by Kirchhoff in his chart, and an infinitude of 
nebulous bands just on the point of being resolved.” .... 2nd. “ That 
the coincidences between the bright lines of the metallic spectra and the 
dark lines of the solar spectrum remain perfect even with this greatly 
increased power.” .... 3rd. 66 That many of the bands of the metallic 
spectra are broad coloured spaces crossed themselves by bright lines. This 
is the case with the orange band of the strontium spectrum, and with the 
whole of the calcium and barium spectra to a remarkable extent.” 
A New Photometer. —An instrument by means of which the exact 
intensity of light can be measured has just been invented by M. Place. 
It is stated that it will enable the photographer to calculate the chemical 
intensity of either natural or artificial light with very great accuracy, 
and thus preserve him from a very common error, that of supposing that 
the beauty of the results obtained are due to the perfect character of some 
new process, when it is really owing to a more favourable light. 
ZOOLOGY AND COMPARATIVE ANATOMY. 
Metamorphoses of Ptcromalus. — The development of Pteromalus (a small 
parasitic hymenopterous insect) was described some years since in the 
“ Annales des Sciences Naturelles,” by Dr. Philippi. The eggs of this 
creature are deposited singly in the transparent ova of a species of beetle, 
and when the young larva appears it is like a small animalcule, an 
infusorian provided with a little tail, which it whisks about rapidly ; its 
