June 22, 1882] 



NA TURE 



177 



Mr. S. E. Peal, I may, therefore, be communicating stale infor" 

 maii .11 ; but as it is the result of personal experience, what I 

 have to relate may be of some use as confirmatory of statements 

 of others. Mr. Peal would not be able accurately to estimate 

 direction, unless the sense of hearing — the capacity to receive 

 sound — was precisely equal and similar in each ear. A greater 

 sensibility in one than in the other, would incline him to the 

 right, or the left, as the case might be. 



Few people know that they may be partially deaf on one side, 

 and yet not perceive it, just as some are right- or left-eyed, with- 

 out knowing it. A good test is a watch slid along a two-foot 

 rule, the end of which touches the cheek. The watch is moved 

 away, inch by inch, till the ticking is no longer audible— if the 

 distance is the same on both sides, the sensibility of each ear is 

 of course equal. 



1 shall not forget my horror when my medical man, applying 

 this test, showed that while with my right ear I could distinguish 

 the ticks far beyond the 2 feet, my left ear was impervious to 

 the sound until within an inch or two of the watch. Hearing 

 on that side has now totally ceased, and the result is / have not 

 (lie slightest idea of the direction of sound. I can hear certain 

 sounds (for I am becoming deaf on the right side also), but to 

 whichever side I incline my right ear, from thence do I fancy 

 the sound to come. 



To me, with my passion for ornithology, it is a terrible 

 deprivation. In my youth my senses were intensely acute. I 

 could instantly detect and proceed to the faintest note uttered by 

 a bird in the forest. Now the loudest call only puzzles me the 

 more. But I was a long time before I found this out. I 

 fancied more than once that the bird I was pursuing had powers 

 of ventriloquism ; then that there were two or more, calling 

 from different directions. As soon, however, as I found, as 

 before stated, that I was deaf on one side, I began experiment- 

 ing on myself, and quickly arrived at the conclusion that in order 

 to estimate direction, both ears needed to be equally sensitive. 



A curious instance of correct judgment as to direction and 

 distance of sound is given by one of the South African explorers, 

 Green, I think. He had been much annoyed by a lion which 

 roared round his camp. Taking his rifle and some of his native 

 followers, he went outside in the direction of the sound. Halting, 

 they listened intently, and at the next roar caught the exact direc- 

 tion, and judged the animal to be at (I think) about 300 yards. 

 Carefully levelling his rifle, he fired, and had the satisfaction of 

 hearing the well-known "thud " of the bullet, and a change of 

 note from the midnight serenader. Next morning showed 

 traces of blood, and following up the track they found, and 

 despatched the wounded beast. 



Colour-blindness is represented in the other sense, by an 

 inability to distinguish certain sounds. That this is caused by 

 partial deafness, 1 am now pretty well certain. My father-in- 

 law, who never knew lie was deaf, never heard the chirrup of 

 the cricket, and I now rind I cannot do so. Only last night my 

 wife observed " what a noise the crickets are making," to me 

 there was unbroken silence as regarded outward sounds. I only 

 heard the continuous " buzzing" that sounds in my bead, aug- 

 mented by the regular "thud thud" of my pulse. 



I have a clock, the hours of which strike on a sweet-tored, 

 metallic bell. If my right ear is turned towards it, at a mode- 

 rate distance, I hear the ringing note ; if turned away, I am 

 only con-cious of the " burr " of the works, and a dull "thud, 

 thud," deno'ing the stroke. AVhy do I hear the "burr,'' which 

 is not so loud, or clear, as the metallic "ting"? That wave of 

 sound seems to pass by and not affect me ; it is like the sharp 

 note of the cricket. 



The cause why certain sounds are inaudible to certain ears is 

 a subject well worthy of investigation, as bearing on the placing 

 of sentries or outposts at night, in time of war ; also for sports- 

 men hunting large dangerous game. E. L. Layard 



British Consulate, Noumea, New Caledonia, April 7 



Jamaica Petrel 



Mr. D. Morris asks (Nature, vol. xxv. p. 151) for some 

 clue to the locality and general character of the nesting-places 

 of petrels. As i fail to find any reply in your pages up to 

 January 19, I venture to send my mite by way of response to 

 Mr. Morris. 



Most of the petrels (JEstrelata), the Storm Petrels ( T/talassi- 

 droma) and the Sheenvaters (Puflinus) breed in holes in 

 the ground, excavated by themseives ; sometimes on small 



islands, at other times on high mountains, at considerable dis. 

 tances from the sea. 1 heir movements to and fro are almost 

 always performed at night, and as they are capable of a very 

 rapid flight, a distance of fifteen or twenty miles is quickly 

 traversed. 



Here, in New Caledonia, the well-known ySstrelata mollis 

 breeds on the summit of Mont Mou (about 4000 feet) in January- 

 March, in great numbers, laying one white egg, as usual. I am 

 informed that in some places the ground is honeycombed » ith 

 their burrows. I am also told that during the non-breeding 

 season numbers come to roost in their old holes. 



The larger, SE. rostrata, Peall, nests in similar places, but at 

 a much less elevation, on the Island of Uen, the most southern 

 portion of New Caledonia, and hardly divided from it by the 

 celebrated Wodin passage. 



Other species are said to frequent other mountains in the 

 interior, but I have no personal knowledge of them. 



In Fiji I obtained Pitffinus ungax, which bred far aw av in the 

 mountainous interior, and there are other true petrels which do 

 the same. 



Vast numbers of various petrels and shearwaters are found in 

 these seas, and I fancy all burrow, more or less, in the earth, to 

 lay their eggs. Of the " Great Grey Petrel " (Adamastor cinerea) 

 Capt. Hutton says, that it "burrows horizontally into the wet, 

 peaty earth" (of Kerguelen's land) "from two to eighteen 

 fee - ." 



That the "Jamaica Petrel" resorts to the Blue Mountain 

 range of Jamaica, for the purposes of breeding, I have not the 

 smallest doubt, and if the holes are examined at the right time 

 of year, I feel sure eggs will be found. The birds probably do 

 U'e the holes as resting places, during certain periods of the year. 

 They do not, however, lay their eggs at sea ! and sooner or later 

 Mr. Morris may be sure of finding eggs, though he may not find 

 much of a nest. 



The breeding of the Mutton Bird (Puffinus brevicaudus) on 

 many of the Australian islands has been often described. Its 

 burrows render walking positively dangerous. If Mr. Morris 

 can refer to Gould's "Birds of Australia," he will find much 

 information on this head. E. L. Layard 



British Consulate, Noumea, April 10 



The Regnard Incandescent Lamp. — In reply to several 

 pyviiespondents who find a difficulty in toe use of petroleum for 

 this lamp, we think they may be more successful with benzoline. 



DOUBLE STARS ' 

 II. 

 "\ "\ T E are in possession of numerous methods of computing 

 * * double star orbits. Sir John Herschel gave one 

 of the first solutions of this problem, and his method has 

 been used more than any other up to this, and so far from 

 becoming obsolete, it is yearly gaining ground at the cost of 

 the methods that have been proposed elsewhere. It starts 

 with the construction of the orbit, which the companion ap- 

 pears to describe round the main star. It is clear that as the 

 planes of the orbits may be inclined in every direction in 

 space, we see only the projection of the real orbits on the 

 heavens, but this, as well as every other projection of an 

 ellipse on a plane surface, is another ellipse, though the 

 main star does no longer appear situated in the focus. 

 Five points determine an ellipse, if we therefore possess 

 five complete observations, we can determine the apparent 

 ellipse. Now the observations are not perfectly accurate, 

 but the calculus of probabilities furnishes us with means to 

 ascertain the most probable ellipse from a great number of 

 observations, to which different weight may be attributed, 

 according to their reliability, as far as known. But at Her- 

 schel's time, though the angles had been fairly observed, 

 the measurement of these minute distances was still in its 

 infancy. He, in consequence, threw them away, and 

 computed distances by aid of the Keplerian law referred 

 to above, from the angular velocities, concluded from a 

 comparison of observations separated by moderate inter- 

 vals. He improved the angles in the following way : — 

 On a paper neatly divided into squares, he lays down a 



1 Continued from p. 155. 



