218 
rorULAR SCIENCE REVIEW. 
Nairn's Electric Machine . — In a paper read before the Royal Academy of 
Belgium, but the report of which reached us too late for our last number, 
M. P<$rard, of Li6ge, read a note on a modification of Nairn’s electrical 
machine, which gives much stronger sparks, and produces much more 
powerful effects, than can be obtained with the ordinary machine. The 
modification consists in suspending a Leyden jar from each of the con- 
ductors of the machine, and connecting the outer coatings of the two jars by 
a chain. The permanent and complete neutralisation of the two coatings 
thus united gives great energy to the condensation. By employing jars 
160 millimetres high and 90 in diameter, M. Perard has succeeded in 
piercing a plate of glass 6 millimetres thick, although the glass cylinder of 
the machine was only 50 millimetres in diameter, and the cushion 380 long. 
In its ordinary state this machine gives a spark which passes between the 
extremities of the branches across a space of 45 millimetres ; but when the 
jars are placed as described, the spark occurs much less frequently, and is 
much louder and more vivid, and can be obtained 100 millimetres long, or 
even 170 when the atmospheric conditions are favourable. This spark has 
not the continuity of that of Holtz’s machine or Ruhmkorff’s coil, but it is 
much more powerful than the first, and may be compared to that of a large 
coil for amplitude and brilliancy. The detonation of the spark 170 milli- 
metres long is as loud as that of the spontaneous discharge of a battery of 
six Leyden jars. 
The Source of Solar Temperature. — Padre Secchi publishes a paper in Les 
Mondes (February 24) on the means by which the solar temperature is 
maintained. Of this the following is a summary : — The sun is a globe 
possessed of an enormously high temperature, undoubtedly reaching many 
millions of degrees ; but our means of estimating that temperature are very 
imperfect. As to the origin of this high degree of heat, it may have been 
the result of the force of gravitation which has united the elements of which 
the central point of the system (viz. of our solar) has been made up ; the 
initial temperature, therefore, the result of mechanical action, will, of 
necessity, have been far greater than the present temperature of the sun is, 
which is certainly cooling down. However great this loss of heat may be, it is 
imperceptible to us, since it is slowly taking place, and partly compensated 
by chemical actions which take place in the sun, which is, in all probability, 
in its interior, a mass of strongly-compressed and condensed nebulous 
matter. 
M. Lumy's New Thermometer'. — At the meeting of the French Academy, 
on Februay 21, M. St. Claire-Deville made a few remarks on a new 
thermometer invented by M. Lamy. Ammoniacal chloride of calcium 
gives off gas which, in a closed space, possesses a tension which is directly 
related to the temperature. If, therefore, a meteorologist places on the roof 
of his house a small metallic box containing sufficient solution of calcium 
chloride saturated with ammonia, and connects it by a leaden tube with a 
manometer in his room, he can observe at any moment, without disturbing 
himself, the external temperature. M. Faye having proposed to apply this 
instrument to the study of subterranean temperatures, M. Becquerel called 
attention to the fact that, five years ago, he had had constructed thermo- 
electric apparatus which perfectly fulfilled M. Faye’s desideratum, and 
