June 23, 1881] 



NATURE 



165 



arriving at the spot. Some ladies describe a remarkable sensa- 

 tion accompanying the proce s : a sort of "alloverishness," or 

 even faintness so much so that the lady fir^t alluded to on one 

 occasion staggered, and omld not proceed at all. 



It appears to me to he a very peculiar p.-ychological phenome- 

 non well worthy of investigation, if possible, but too well known 

 to be disputed. George Henslow 



6, Titchheld Terrace, Regent's Park, N.W. 



P.S.— Since writing the above I have heard of a much more 

 remarkable case than ihe preceding. The operators sat in a 

 circle, silent, but determinately "willing" that a certain lady 

 should do what they had resolved upon. She stood in the centre, 

 and was not blindfolded or touched by any one. In every case 

 she did it correctly. One thing that was agreed upon was for 

 her to take a bottle of wine from one table, carry it to another, 

 and pour out a definite quantity of wine. This she did, not 

 exceeding the amount predetermined. On a second occa.sion she 

 had to find a key hidden away behind some books. As she 

 approached the place she became very excited and hysterical, but 

 at once extracted the key. 



The above cases clearly show that as far as they are concerned 

 " thought reading " is an incorrect expression, as the person 

 operated npon is a passive automaton, %\ hile others, as it were, 

 force their wills upon her. " Will-imparting" would seem to be 

 a better term. — G. H. 



Notes of the Cuckoo 



In a letter appearing in Nature, vol. xxii. p. 76, I stated 

 that — " All the cuckoos here intone in a minor key except one, 

 which aloi e does not flatten the 3rd of the tonic. The key is in 

 all cases j recisely D of concert pitch, as proved by a tuning- 

 fork, and the first note is F on the fifth line." This year I find 

 that, while the cuckoos here generally intone in D minor, as above, 

 there is one again that intones in D major, and two others in C 

 major and C minor respectively. Some that I casually heard in 

 other places in the neighbourhood intoned in D minor. 



Millbrook, Tuam, June I John I'irmingham 



Notes on the Indian GIovy-Fly 



Having failed to find any critical description of these inte- 

 resting insects, it vs possible that the notes I am now able to send 

 you may cause others to enter the field of inquiry. Situated 

 some 2900 feet above the sea, .and in Cen'ral Southern India 

 amidst hills, valleys, and streams, I have had peculiar opportu- 

 nities for observing them. 



They are not to be seen during the daytime, but so soon a.s 

 darkness steals upon twiliijht, ;o surely do these small natural 

 lanterns become visible, and their numbers rapidly increase, 

 much indeed as the visibility of the .stars increases as the evening 

 passes into midnight. 



The fire-fly, when examined individually, is by no means a 

 pretty-looking insect, and comparing it to other insects and flies, 

 it is certainly both large and ungainly. An ordinary house fly is 

 five-sixteenths of an inch in total length and weighs -25 grains, 

 but the subject of my notice has a total length of nine-sixteenths 

 C'f an inch and weighs "66 of a grain ; we thus at once learn 

 something as to his size and weight. The glow-fly — or beetle as 

 I should term it — has a black head and antennae ; the thorax and 

 abdomen are of a yellow-red colour. This latter part of 

 the insect's body is divided ii.to six rirgs, and, counting from the 

 thorax, it is the fourth ring that emits the light. There is a 

 rectangular opening in this ring which is merely covered by a 

 very thin skin ; it is in fact a window from which the light 

 emerges. The insect has only one pah: of win^s : these are 

 small, most delicate and thin, and are sheathed. It is worthy 

 of careful notice that these insects fly both rapidly and slowly, 

 but make no noise or buzz in the air. To test this further I have 

 frequently liberated several of these glow-beetles in my bed- 

 room, and in the dark they have only appeared as fairy stars, 

 as no humming could be detected. 



As regards the character and quantity of the light, I have to 

 observe that one insect enables me to see the time by a white- 

 faced wafdi when four inches distant ; twelve of them placed in 

 a glass jar enable me to read a book w ith ease, and are equal to 

 a small Geissler's tube. The light is of an exceedingly bciutiful 

 colour — a sombre yellow tinged with green, but at iiitervals it is 

 brilliant. A preliminary examination of the light in the spec- 

 troscope (a large one made for me by Browning) shows a distirct 



clear continuous spectrum, no lines or bands of any kind being 

 visible. 



The insect made to crawl on a card placed over the poles of a 

 powerful compound permanent magnet showed no signs of un- 

 easiness or change of light. Similarly placed over an electro- 

 magnet (ten Grove cells) and rapidly alternating the current caused 

 no change. Placed within a coil of covered wire, no change. 

 Blowing very gently, my breath on the insect caused no 

 change ; this was also tried w ith a blowpipe. Cold air at 50° 

 caused a distinct diminution of the light ; on the other hand, air 

 at 100° cau-ed an increase of light. 



I now placed several of the insects in a bell-jar, and gave them 

 a good supply of clean oxygen gas ; the luminosity at once 

 increased fully 25 per cent. On a dead insect (which still sheds 

 light) oxygen gave similar results, and on extracting the luminous 

 part and' blowing oxygen upon it the light was much increased. 



It will prove interesting to mention that, so soon as darkness 

 has fairly set in, millions of these insects invade the trees, 

 and as my bungalow is near to a stream and level w ith the tops 

 of the trees, I am able to notice them w ith much care. The 

 curious pulsation or flashing of their light is remarkable : the 

 insects resting on the tree all act in perfect concert, i.e. five 

 seconds of no light, then seven rapid flashes ; five seconds, no 

 light, seven flashes ; and so the game continues throughout the 

 dark hours. 



At first I had reason to believe that the insect when flying 

 only emitted light; this however is not the ca.e; for v\ hen 

 observing the Pole Star for variation with my theodolite, it 

 occurred to me during a passing cloud to turn a telescope on to 

 the glowing tree. At once I had the field of view filled with 

 tiny stars, but both fixed and wandering. 



It is .ilso worthy of special notice that all the glow-insects on 

 a dozen or more trees will continue to keep up the most perfect 

 time as to the flashing of their light and the interval of pause, 

 and this for many consecntive hours ; but this singu'.ar agreement 

 as to the time relates to close clusters of trees only. Thus distinct 

 groups of trees separated by one or more hundred yards may 

 not agree, and do not do so as a rule. 



I have been informed on safe authority that the Indian bottle- 

 bird protects his nest at night by sticking several of these glow- 

 beetles around the entrance by means of clay ; and only a few 

 days back an intimate friend of my own was watching three rats 

 on a roof rafter of his bungalow when a glow-fly lodged very 

 close to them ; the rats immediately scampered off. 



In conclu ion, these insects see by day as well as by night, 

 and I incline to the idea that the beautiful light they can7 

 serves as a means of intimidation or protection, and certainly as 

 a means whereby to recognise friends. 



As I gaze from my verandah down the Nadgani Valley into 

 the dark night I see the pulsations of light here, there, and 

 everywhere! and as my optical powers increase so do these 

 easeous, nebulous patches become resolved intj real living 

 ftars ! H. A. Severn 



Wynaad, India, May 5 



Birds Suffering from Cold 



The unusually severe weather (5° - 12° Reaumur) of ahese 

 last twelve days struck heavily on the swallows of our counti7. 

 They have been found dead by hundreds. The distress of the 

 poor animals must have been extreme. Suff'ering from hunger 

 and cold, they pressed against the windows, and being brought 

 in suffered to be petted and fed, but died from exhaustion. In 

 Kopidlno about 300 took shelter under a balcony, and the 

 cold growing more ard m^ re intense towards night, they 

 clustered on each other like bees niuil m. rning, when thirty 

 were f. und dead. I have been walking this afternoon in the 

 .suburbs of Prague, wheie a fortnight ago I have seen swallows 

 skipping on the river and hunting in gardens, but although the 

 weather'was now clear and warm, I could not see a single one. 

 Tidings of suffering swallows come from the countr)', where 

 people have been kind to them, feeding them on ants' eggs and 

 flies but they would not eat, and died. In some nests the young 

 ones were found starved alone, in others their mothers werewiti 

 them. J- V. SLADEK 



Prague, June 16 



An Optical Illusion 



Thf illusion of the inverted pin was shown me about the year 



1846-47, and I well remember, when I was at Cambridge, 



