y^inc 13, 1872] 



NATURE 



ties. Taking the specific heat of air to be o'267, as at 

 that time determined by the observations of De la Roche 

 and Bcrard, he found the dynamic equivalent of an 

 unit of thermic energy to be 367 dynams. But if, in the 

 calculation of this number, the more careful and accurate 

 subsequent determination of the specific heat of air by 

 Regnault be substituted, namely, o'2375, the result gives 

 as the equivalent 426 dynams ; a result almost identical 

 with that of Dr. Joule, but based on purely theoretical 

 considerations. 



Subsequently M. G. A. Hirn* pursued a course of 

 observations exactly the reverse of that of Dr. Joule, 

 namely, to determine the amount of heat converted into 

 work in the steam-engine. Taking it as an axiom, which 

 he showed to be in strict accordance with analytical in- 

 vestigations, that the difference between the heat existing 

 in the steam as it enters the cylinder and that remaining 

 in it after its exit, must be the thermic equivalent of the 

 work done in and by the engine (which difference in the 

 best constructed engines amounts to about 5 per cent, of 

 the total heat due to the combustion of the fuel), he de- 

 termined the value of one thermic unit to be 425 dynams; 

 a remarkable result, and intermediate between those pre- 

 viously obtained by Mayer and Joule. In the face of such 

 overwhelming concurrent evidence will even the reviewer 

 be still bold enough to assert that the consei-vation of 

 energy is a myth .' 



The principle of the dissipation of energy, as a corollary 

 to that of its conservation, is of course equally ignored by 

 the reviewer ; but as his remarks on that point have no 

 relation to anything beyond his own inner consciousness, 

 it must here suffice to give a familiar illustration both of 

 the conservation and the dissipation of energy, in the 

 action of the rifle-ball. This reaches the target with less 

 velocity, and consequently with less energy, that it pos- 

 sessed on leaving the muzzle ; a portion of its energy 

 has been expended in producing heat by friction 

 against the particles of air between which it passes, which 

 is dispersed through the surrounding atmosphere, 

 and thus becomes dissipated. On reaching the tar- 

 get the progressive motion of the mass is arrested, 

 and converted into molecular motion, which is cog- 

 nisable only as heat, by which the mass is reduced to 

 the fluid state, and splashes of molten metal are scattered 

 in all directions. These again impart their heat partly to 

 the air through which they pass, partly by radiation into 

 space, and partly to the ground on which they fall ; and 

 thus the whole energy of the ball becomes dissipated. An 

 analogous explanation will apply to all other cases of the 

 dissipation of energy ; thus the principle may be inde- 

 finitely illustrated, but it is hoped that it has now been 

 sufficiently established that the conservation of energy 

 is a fact, not a " heresy of science," the reviewer's opinions 

 to the contrary notwithstanding, for 



A man convinced against his will 

 Is of the same opinion still. 



Want of space forbids the consideration of the larger 

 cosmical relations of the conservation of energy to both or- 

 ganic and inorganic existence ; one proposition only shall 

 be alluded to as having been by some writers rather over- 

 strained, viz., that the amount of energy in the world is 

 unchangc-ble, the sum of the actual or kinetic and poten- 

 tial energies being a constant quantity. This may be 

 taken as a postulate, and is probably true, but it is a 

 proposition that is equally incapable of proof or of dis- 

 proof, because the amount of potential energy in a body 

 can be determined only by its development into actual 

 energy, and cannot therefore be predicated. For example, 

 two stones of equal weight lie one at the bottom of a well, 

 the other on the ground at its edge ; both are raised and 

 placed side by side on the top of the windlass frame, 

 much more work has been done on one than on the other, 



but can any one predicate in which of the two the greater 

 amount of potential energy resides ? Or is there any 

 conceivable difference in the amount of energy acquired 

 by either, otherwise than as dependent on its descending 

 through the greater or the lesser distance ? 



It may, in conclusion, be remarked with much regret that 

 the principle of the conservation of energy has by some 

 been misapplied in a fruitless endeavour to supersede the 

 necessity of a creative intelligence. To the mind of the 

 writer, and, it is earnestly hoped, to that of most of his 

 readers, the indisputable estabhshment of this principle 

 conveys only a more exalted idea of that infinite wisdom 

 by which the perpetually recurring transformations and 

 interchanges, not only of the materials, but also of the 

 powers, of Nature are rendered subservient to predeter- 

 mined laws, which govern the comfort and welfare of all 

 created beings, CHARLES Brooke 



SPECTROSCOPIC NOTES" 



ALTHOUGH P. Secchi and others have recently pub- 

 lished descriptions of the difierent varieties of solar 

 prominences which have been observed, well illustrating 

 the many forms in which these outbursts from the sun's 

 chromosphere occur, a careful record of such disturbances 

 as may be out of the more common order may in the end 

 assist us to a further knowledge on this subject. 



While looking for bright lines near F in the spectrum of 

 a low prominence situated 25° north of east, at 11.35 A-*'- 

 (April 2), my attention was called to what appeared to me 

 a sudden displacement of the F line toward the violet end 

 of the spectrum. 



I immediately brought the C line into the field of view, 

 in order to discover if any change was taking place in the 

 form of the prominence, but was wholly unprepared for 

 the spectacle which met my eye. Upon widening the 

 slit I found that where only twenty minutes before there 

 had been a comparatively low mass of prominence matter 

 not exceeding 50" in height, and remarkable only for the 

 brightness of a jet issuing from the southern portion which 

 was but slightly raised above the chromosp'nere, there had 

 been an eruption of matter on a grand scale. 



Fig. I represents the prominence as first seen at 11.15 

 A.M. At 11.35 A.M. the northern portion had entirely dis- 

 appeared, and from the low mound, at the point where the 

 jet mentioned above had been seen, an eruption had taken 

 place far exceeding anything I have ever witnessed. Far 

 above the chromosphere the air was filled with long 

 wisps of glowing hydrogen, ranging from 20" to 50" in 

 length, with the appearance of having been ejected in 

 quick succession. Above them floated detached masses, 

 in the form of thin fleecy clouds, and the highest point 

 reached by these was fully five minutes of arc, or about 

 135,000 miles above the sun. In the mound appeared a 

 low, sharp horn, exceeding in brightness any other portion 

 of the prominence. The grandeur of the eruption lasted 

 but a few minutes, gradually fading in brightness and 

 diminishing in size. 



Fig. 2 gives a correct idea of the general form and ex- 

 tent of the prominence as seen at 12 m. 



When next observed at 1.40 p.m., nothing was left but a 

 small cloud mass of about the height of the prominence 

 when first seen, at JI.15 a.m. To the north of this, how- 

 ever, were two very small horns, of great brightness. It 

 has generally been noticed that the appearance of these 

 bright points in the chromosphere is a forerunner of in- 

 creased activity. The forces at work beneath were only 

 gathering strength for a final outburst, which, if not so 

 great in extent, proved to be equally magnificent. I had 

 not long to wait ; for after a few minutes spent in examin- 

 ing theF line, just as the clock was striking the hour, I 

 again brought C into the field, and found myself only in 



* Reprinted from advance sheets of the Journal of the Franklin Institutt 

 funiished by the £ditoir. 



