NATURE 



{May I, 1879 



4 



accommodate which the order Pala:odictyoptera has been formed. 

 It is not for me to here enter into an examination of the mate- 

 rials incUided in this so-called order. It will suffice to say that 

 not one of them could be suspected of being lepidopterous. 



The point at issue is, did anthophilous insects (and therefore 

 flowers also) exist during the carboniferous epoch ? According 

 to my views we are without evidence of their existence. 



I decline any further discussion on this subject until Mr. 

 Wallace has examined the fossil, or has obtained evidence of 

 its peculiarities from some one in whose judgment he has more 

 confidence than he apparently has in mine. 



Lewisham, April 25 R. McLachlan 



Captain Cook's Accuracy 



In Nature, vol. xix. p. 408, there is an article entitled 

 " Captain Cook's Accuracy," which 1 think reflects unjustly upon 

 the late Admiral Wilkes, U.S.N. As a specimen of Wilkes's 

 inaccuracy the writer of the article cites first the discrepancy in 

 the position of Turtle Island, the south-easternmost of the Fiji 

 group. Cook and Wilkes differing more than 30' of longitude. 

 The narrative of the U.S. Exploring Expedition was written on 

 board ship during the progress of the work, and was placed by 

 Wilkes in the hands of the printer immediately upon his return, in 

 order that the general results might be known without delay. The 

 astronomical positions v\ ere given as they were recorded at the 

 time, and were not corrected for final chrononietric errors and 

 rates, which were carefully ascertained while the charts were 

 being prepared for publication. A comparison of the narrative 

 with the atlas, published subsequently, will exhibit diflferences of 

 longitude almost throughout. 



On the general chart of the Pacific, sheet III., which is on a 

 very small scale, so that a slight inaccuracy of the draughtsman 

 or engraver will cause a difference of several minutes, Turtle 

 Island will be found to be in about 178° 22' W. long., but the 

 special plan of the island (vol. 2, p. 94, of the Atlas) places it 

 in lat. 19° 47' S., and long. 178° 16' iS" W., while Capt. Den- 

 ham, R.N., in 1856, places it in 19° 49' ll' S., and 178° 14' 42" 

 W., where it is at present shown on the British Admiralty Charts. 

 The difference of latitude is about I' 45" ; that of longitude, 

 l' 36"; differences which might readily be accounted for by 

 different points of observation having been used. The difference 

 in the outline is not very material. 



As Cook placed the Island in 178° W., he was fifteen 

 minutes in error ; wliile Wilkes differs from the latest surveys 

 about a minute and a half. Capt. Worth, of II. M.S. Calypso, 

 in 1848, placed the island in 178" 8' \V., differing seven miles 

 from the subsequent survey by Capt. Denham, the position by 

 the latter being now borne on the British Admiralty chart, yet 

 the former authority is quoted to prove the inaccuracy of Wilkes's 

 work. 



Findlay, judging from what he siys upon this subject, con- 

 sulted Wilkes's book, instead of his chart, which was published 

 subsequently. The second example of Wilkes's inaccuracy, 

 cited by the writer, is that he found from a position which he 

 occupied at Savaii, a trend of coast differing from that as shown 

 by Wilkes's chart, but it is a question whether he was not mis- 

 taken in the identity of the point occui>ied by him. The waters 

 of the Samoan gr )up are, so far as we know, navigated safely 

 and alinost exclusively with Wilkes's charts. 



The third and last example is concerning Quiros Island 

 (Swain's Island). The facts in this case are that the boats of 

 the exploring expedition did not effect a landing on the island at 

 all ; efforts were made to do so, but were unavailing on account 

 of the surf, so that it is quite impossible that they could report 

 the existence of a lagoon hid from their view by a wooded strip 

 of land even if only a quarter of a mile in width. 



In criticising the work of such explorers as Cook, Vancouver, 

 and Wilkes, it should be borne in mind that the expeditions which 

 they commanded «ere for exploring rather than surveying pur- 

 poses, and it is rather a matter of surprise that they should have 

 come so near the truth when we consider the crude materials 

 with which they had to work. S. K. Fkanklin 



Hydrographic Office, U.S. Navy, Captain U.S.N, and 



Washington, D.C., April 11 Ilydrographer 



Sense of Force and Sense of Temperature 

 "J. T. B.'s" "discovery" of the distinction between muscular 

 sensations— or, as he styles them, the " sense of force," whatever 



that may mean — and the sensation of temperature, has been long 

 anticipated by Alexander Bain in his work on "The Senses and 

 the Intellect. ' 



Again, your correspondent's illustrations of the distinction he 

 draws between absolute and relative muscular sensations and 

 sensations of temperature are wholly illusory. How can it be 

 said that a letter-sorter enjoys and improves absolute sensations 

 of weight ? Surely his sensations enable him to determine not 

 "absolute weight" (whatever that may be), but the weights of 

 particular letters relative to certain standards, according to which 

 relation the postage is charged. These sensations enable him 

 to say that certain letters are over, and others under, an ounce 

 in weight, and thus they are in fact relative, not absolute, as 

 " J. T. B." seems to suppose. 



The same remarks apply to " J. T. B.'s " assertion that "the 

 sense of temperature may also be rendered absolute to a certain 

 extent," and to his illustration of the plumber who judges 

 whether the heat of the soldering-bolt is adequate for his pur- 

 pose. Here again the sensations are, in truth, purely relative, 

 any inference drawn from them being based Uiion a comparison 

 of present and previous sensations and present and previous 

 experience of their results. A. K. R. 



Mark Lane, April 23 



Mr. Preston on General Temperature-Equilibrium 



My attention has been arrested by Mr. S. Tolver Preston's 

 paper on general temperature equililjrium in Nature, vol. xix. 

 p. 460, and by a letter from him in a later number (p. 555), 

 pointing out a trifling literary ambiguity in it. As this implies 

 that the paper is otherwise correct, you will perhaps allow me 

 to protest, and to state that it is full of confusion of reasoning 

 and of unsoundness. 



I do not know how many sins against dynamics could be dis- 

 covered by careful examination, but at least two pervade it 

 throughout, viz. (l), the assumption that the simple relationship 

 which exists between the movements and the temperatures of 

 molecules of matter exists also between the movements and the 

 temperatures of masses of matter ; (2) the assumption that 

 gaseous molecules (simple or compound) whose bond is chemical 

 alTiiiity differ mechanically from masses of matter (stellar or 

 otherwise) in size and weight only, whereas they really differ in 

 a multitude of other ways, and notably in elasticity ; and from 

 this difference alone it would be easy to show that the analogy 

 in the paper is fanciful, and its reasonings and conclusions 

 invalid, but I respect your space. 



In conclusion I would say that I am not writing against the 

 hypothesis of temperature-equilibrium itself. It may or may 

 not be true. All I assert is, that this paper gives no real in- 

 formation about it. Wm. Muir 



'33. Upper Thames Street, E.C., April 26 



The Migration of Birds 



It was becau e I'rof. Newton mentioned such distances as six, 

 seven, and ten miles {vide Nature, vol. xix. p. 434), in connec- 

 tion w ith the flight of migratory birds, that I brought forward 

 the matter of temiierature, and the latter still appears to me to 

 have as much bearing on the question, as has the density of the 

 atmosphere. 



The intense frost on Christmas eve, 1861, was said to have 

 killed a large number of thrushes, blackbirds, &c., in Scotland. 

 Near Edinburgh, where the thermometer registered about - 4''F. 

 during the night, many dead birds were found. These deaths 

 resulted from cold, not from starvation, for the weather was 

 oi)en until within a few days of Christmas day. Now, if a frost 

 of this severity has such an effect on bird-life, surely it must be 

 conceded that temperatures from - 25* to - 100° F. — those that 

 would reign between six and ten miles' elevation, with surface 

 temperature of -t- 80° K. — would slay the hardiest migrant. 



There is a great difference bctw cen the elevation required to 

 view a distant sea horizon, and an equally distant mountain-top. 

 For instance, to obtain a sea-horizon of 300 miles, you must 

 mount nearly twelve miles ; but from an altitude of four miles, 

 the summit of a mountain 20,000 feet high (less than 4 miles) would 

 be visible, though its base lay 300 miles ofT. Similarly, if an 

 elevation of 5,000 feet only be granted to the haze that constitutes 

 the loom of land, birds flying two miles high will have a circle of 

 vision, for the land indication, of over 200 miles radius. Under 

 such circumstances, if the journey is 1,000 miles in length, a 

 deviation of some 12° on either side of the true direction of flight 



