142 



NATURE 



\yune 20, 1872 



made his case in one respect so strong as it might be. In the 

 passage "nunc ignes sa;pe (lammati caiincas cidinimim crislas 

 superjecto favillai urn monte tumulabant " (as the ediiion which 

 I follow has it) he translates ciilmina "roofs," and again in the 

 parallel passage of Avitiis. I think it more likely to mean 

 summits (of mountains), and to refer to the formation of one or 

 more new cones in the hill country. 



My reason for this may be given in the words which I used in 

 the paper above named — " though Sidonius is inclined to bombast, 

 he scarcely seems equal to a flight like this. ... In the 

 parallel passage in Avitus, the reference to Isaiah ii. 10, 19, 

 21, and I.uke xxiii. 30 appears too clear to allow any other 

 meaning than mountain-top to be assigned to culineu." To this 

 I may add that the ridge-roofs, frishr culinimim, would be those 

 least likely to be broken by a shower of ashes, and the ridges 

 would be the part where the smallest quantity of ashes would 

 fest. T. G. EoNNEY 



St. John's College, Cambridge 



Force and Energy 



Referring to Mr. Brooke's article in Nature of the 13th 

 on Force and Energy, I would suggest that though it is quite 

 true that heat is a " mode of motion," this is probably not true 

 of magnetism and static electricity. Heat is molecular motion, 

 magnetism and static electricity are molecular tensions. 



I would also remark that tlie term "radiant heat " ought to be 

 discarded as misleading. Radiant heat is not a kind of he.it ; 

 it is quite distinct from heat, but it is nearly identical with li^ht. 

 "We ought to introduce the word radiance, and then we get to 

 this statement :— All rays of radiance have more or less heating 

 power, and some of them have also the power of producing tlie 

 sensation of light. But the foct that only some rays, and not 

 those whicli have the most heating power, produce the;^sensation 

 of light, belongs rather to the retina than to the rays. 



Mr. Brooke thinks the proposition that the sum total of 

 energy in the universe is unchangeable is incapable of proof. I 

 do not speak as having any authority, but it seems to me tliat if 

 this is not true the conservation of energy cannot be universally 

 true. JosEni John Murphy 



Pelagic Fish-Nest 



Seeing an extract from Nature with reference to the nest of 

 the pelagic fish, allow me to inform you of the discovery of what 

 I presume to be a similar nestinlat. 25° N., long. 65°W., whilst on 

 a voyage between Uuenos Ayres and New York last January. I 

 had improvised a drag-net out of a barrel hoop and a biscuit bag, 

 to fish up for examination the straw-coloured floiting gulf-weed, 

 which covered the sea in long lines and patches between 20° and 

 32°N. lat. ; and one day there came up in the net amass of weed 

 compactly woven by strong, white, sdky fibres into a round ball 

 of about ten inches in circumference. Tlie surface of this Ijall 

 was covered with a network of these fibres, to which large nurr.- 

 bers of glassy eggs, about tlie size of partridge shot, were at- 

 tached. The eggs were transparent, and their cases very tough. 

 The only living inhabitants of the ball were one or two small 

 shrimps and a small crab, who was carrying his own particular 

 egg-sac. 



Another curious fact I am tempted to mention. About 200 

 miles from Cape Frio, the sailors caught a dolphin, which had in 

 its stomach twenty pieces of coal, varying from a large walnut to 

 a marble in size, together with the heads of four iron nails about 

 an inch in length each. I am tolerably certain tliat these articles 

 had not been thrown from our vessel, but they did not appear 

 affected by the internal wear and tear, however long they miglit 

 have been digesting. George J. Hinde 



Toronto, Canada West, May 18 



Why are Red Sandstones Red ? 



I, HAVE lately been interested in the reply to this question 

 given by Prof. Ramsay, and stated by Prof. Geikie in his recent 

 edition of "Jukes's Manual of Geology" (pp. 567, 56S). 

 But the 'explanation, viz., that the red colour is derived from the 

 precipitation of red (consequently anhydrous) peroxide of iron 

 in inland seas, appears to me to give rise to this other question — 

 Why should the precipitaled peroxide be anliydrous, and not 

 hydrous and brown, as is the case with limonite, which is fouiid 

 deposited in marshes, ponds, and lakes? 



I have tried some experiments in precipitating the peroxide 

 of iron from a solution made as saturated as possible by long 



boiling of water or oxide of iron (obtained from a natural spring), 

 common salt, and finely divided sulphate of lime (these last two 

 minerals being found to accompany the red rocks), filtering hot, 

 and allowing to stand till cold. For want of experience in these 

 matters, probably, I have not yet succeeded in obtaining any 

 red colour. 



I have, however, to-day fallen on a paper describing a similar 

 experiment to account for the presence of anhydrite in the .Stass- 

 furt mines. In this case it is stated that the aniiydrons sulphate 

 of lime was obtained on evaporating a concentrated solution of 

 gypsum and rock salt. 



I should be glad to learn whether the attention of any of your 

 readers has been drawn to this question, and whether they have 

 succeeded in obtaining (under conditions analogous to those of 

 an evaporating inland sea) a precipitation of the red colouring 

 matter. A Young Geologist 



Mounting of Thermometers 

 I HAVE experienced precisely the same inconvenience as that 

 mentioned by iSIr. Whipple in Nature last week. 



I several times removed the outside case of a thermometer 

 such as he describes, and took every precaution to dry the air 

 before replacing the packing, but the moisture in the tube per- 

 sistently reappeared. It then occurred to me that the amount of 

 moisture was out of all proportion to the quantity of air confined, 

 and that the mischief arose from the packing not being air-tight ; 

 and fresh damp air was tints continually finding its way into the 

 tube, and depositing moisture. Accordingly the tube was again 

 removed, and after drying carefully, I replaced it, and pushed in 

 the india-rubber packing about an eighth of an inch. The in- 

 tervening space was filled up with common putty, which was 

 made to assume a conical form round the thermometer stem. 

 After being left for a day or two to harden, the putty was painted 

 over with two or three coats of sealing-wax dissolved in alcohol. 

 This thermometer has been constantly exposed on the grass for 

 about four months, and though I purposely took no means to 

 dry the air in the case, not the slightest inconvenience from 

 a deposition of moisture has since been experienced. 



Reginald Bushell 

 Hinderton, Neston, Cheshire, June 17 



A Few Millions 



In your reprint of Prof. Mayer's paper, entitled " Acoustical 

 Experiments" in Nature for May g, iS72,thereoccursomestrange 

 numerical errors, which perhaps it will be well to point out, lest 

 some of your readers should make use of the numbers given at the 

 end of the paper without previously testing them. After describ- 

 ing his experiments, he proceeds : — " We will now examine the 

 analogical phenomena in the case of light : — Let fork No. I, giving 

 256 vibrations a second, stand for 595 millions of millions vibra- 

 tions a second, which we will take as the number of vibrations 

 made by the ray Dj of the spectrum." Taking the velocity of 

 light as 185,300 miles per second, and the wave-length of D,, 

 as given by Angstrom, at O'OOOjSgso millimetres, gives 

 5,058,700,000,000,000 vibrations per second, or a little more 

 than live thousand millions of millions, instead of a little less 

 than six hundred millions of millions vibrations per second, as 

 given by Dr. Mayer. But to proceed — "Then fork No. 3 will 

 represent 590 millions of millions vibration per second," this 

 should be 594 millions of millions vibrations, ' ' which give a wave- 

 length '0000042 millimetres longer than Dj." This again is not 

 quite right, even according to Dr. Mayer's ownshowing ; it should 

 be '00000495 "^f ^ millimetre longer than Dj. Dr. Mayer then 

 goes on to say that such a wave-length nearly corresponds with an 

 iron line situate '42 div. below Dj on Angstrom's chart ; and 

 ' ' we saw that fork No. 3, giving 254 vibrations a second, had to 

 move toward the ear with a velocity of 8'734ft., to give the note 

 produced by 256 vibrations per second emanating from a fixed 

 point ; so a star sending forth the ray which vibrates 590 millions 

 of millions a second will have to move toward the eye with a 

 velocity of 28,470 miles per second to give the colour produced 

 when ray Dj emanates from a stationary flame." This again, 

 according to Dr. Mayer's own method, shouhl be 1,557 miles, cr 

 less than a nineteenth of the velocity given by him. 



Instead of involving ourselves in millions of millions, and the 

 translation of millimetres into Englisli miles, it seems simf ler to 

 avoid the calculation of the number of vibrations per second, and to 

 get at the required velocity by a simple rule-of-three sum, thus : As 

 the emitted wave length is to the difference between the observed 



