HARDWICKE'S SCIENCE-GOSSIP. 



263 



momentum than air-bubbles would have) run rapidly 

 over the surface, diverging in straight lines (on a 

 calm surface) from the point of contact. I have 

 seen them glide rapidly for many feet over the surface 

 of a mill-pool. The waves of the sea may be often 

 seen to be covered with them, darting in various 

 directions. I'hey have the appearance of beads of 

 glass, and as soon as they lose a certain momentum 

 immediately disappear, being absorbed into the main 

 body of liquid. Is their separate existence main- 

 tained by a thin plate of air interposed between 

 them and the surface of the water, &c., on which 

 they roll ?— 6^. W., Jiiu. 



Density of Sea-water. — Your correspondent 

 ^Ir. Macco admits the probability of misquotation, 

 misprint, or slip of the pen, which is precisely that 

 to which I desired to call attention. In doing so, the 

 giving of "kind advice'" I quite disclaim, nor did I 

 think it courteous or otherwise desirable to assume in 

 your previous correspondent either ignorance or for- 

 getfulness of the elementary facts connected with the 

 subject, with which, I suppose, all the world are 

 sufficiently familiar. — C. F. IV. 



Blackbird and Thrush. — About the middle of 

 last April, as I was looking round the garden, 

 I found a nest nearly finished, which I thought be- 

 longed to a blackbird, but I could not see the female 

 bird. Two days after, looking into the nest, I found 

 four eggs, all just like a blackbird's, except that one 

 egg had the deep claret spots of a thrush ; the female, 

 being still very wary, had flown away before I could 

 see her. Two or three days after, I again visited the 

 nest and found that the bird sitting was a thrush ; 

 she was then very tame, for she let me watch her, 

 standing within a few feet of her nest, and showing 

 no signs of fear. The last week in April the eggs 

 were hatched. I was unable to watch her again for 

 ten days when, to my regret, I found only one young 

 bird remained. The old bird was then very restless, 

 flying all round me, but never going more than ten 

 yards from her nest, and uttering incessantly a single, 

 low, plaintive note. I had then ample opportunity of 

 watching her, and can state with certainty that she 

 was a Song Thrush {Tiirdits nutsiciis). As soon as 

 •ever the young bird was able to fly, both the mother 

 and her offspring disappeai'ed. I saw the blackbird 

 come and sing to her once, standing on a tree close 

 to the nest. I see no reason why this blackbird 

 should mate with the thrush, as there are plenty of 

 blackbirds all around us, so that it could not be for 

 want of one of its own species. Perhaps some of 

 the correspondents of Science-Gossip will kindly 

 give me some information on this subject. — G. T. B. 



Spawn of Newts. — I have found the eggs of 

 newts, not wrapped up, but deposited on stones or 

 other convenient objects. Several of these I pre- 

 served until they were hatched out, when they fed 

 freely on entomostraca, which they would catch by 

 first lying still and then suddenly darting upon them. 

 As the bodies of young newts are very transparent, 

 many of your readers would doubtless find them to 

 be interesting objects for observation during the 

 coming spring. — T. C. 



North Winds.— Before this question can be 

 answered, it must be known whether the plants facing 

 the north are situated on elevated ground and those 

 facing the south in a valley, for if so it is quite in 

 accordance with experience that the latter should, 

 during calm serene nights, suffer from frost, although 

 facing the south, whilst the former, under similar 

 conditions of sky and air, would escape, in conse- 

 quence of their position affording them a higher 



temperature, although on the north side of a hill.— 

 C. C. Haviland. 



The Sun.— The "little black balls rising out of 

 the sun," observed by " Pater," were no doubt the 

 eff"ect of the insensibility to light produced on the 

 retina by gazing at the sun. If one looks at the sun 

 for a second or two, and then looks away, a black 

 spot of about the same size as the sun will be seen. 

 A similar effect is produced by looking at a red wafer 

 on a sheet of paper ; only in this case the spectral 

 wafer appears of the complementary colour, green. 

 I have observed the phenomena mentioned in his 

 second query, — that plants on the north side of a 

 garden are often less injured by frost than those on 

 the south side. This is probably due to the fact that 

 they are more screened from the sun. Plants often 

 suffer not so much from frost as from alternations of 

 frost and sunshine. — R. H. N. B. 



"Alkanf.t.— This plant yields a red dye. The 

 name seems to have been transferred from the Arabic 

 name of another plant, also yielding: dye, called 

 Henna:' 



NOTICES TO CORRESPONDENTS. 



To Correspondents and Exchangers. — As we now 

 publish Science-Gossip at least a week earlier than hereto- 

 fore, we cannot possibly insert in the following number any 

 communications which reach us later than the Sth of the 

 previous month. 



J. H. (Idle, near Leeds). — Theslide you sent us of Diatoms 

 found at New Brighton, contains Rhabdonema arcuattiin, 

 R. iin'nutiim, and Navicula libellus. 



J. French.— You had best get the volumes on " Humming- 

 Birds" (illustrated), price gs., published in the "Naturalist's 

 Library," Hardwicke & Bogue, 192, Piccadilly. They will fur- 

 nish your American friend with all the information he wants. 



T. P. B. — The specimen you sent is the chrysalis of the 

 Death's-head Moth i^Acheroittia atropos). 



C. C. (Coventry). — The specimen you enclosed in the enve- 

 lope is an umbelliferous plant, Astraiitia juaj'or. 



H. A. Francis. — No small tube containing Diatoms has as 

 5'el reached us. 



_H. J. R. Oyestbury). — Origanum vulgare, frequent in 

 Limestone districts. 



A. H. B. (Wallingford).— Gipsy wort, or Lycopus EuropcEus, 



J. P. G. — You are quite right ; it is Hahejiaria alhida. It 

 differs much in size, and frequently the flowers are but faintly 

 perfumed. 



J. B. B. (Dudley). — It is Spifcsa salici/olia. Borrer believed 

 it to be naturalized in the locality where you found your speci- 

 men. We have seen it both luxuriant and abundant on the 

 margin of Lake Miosen, Norway. 



A. P. (Doncaster). — The seedling fern is Cysiopteris fragills. 

 It does sometimes produce bulbs on the margin of the pinnules. 



C. U. (Croydon). — Your specimen is merely the bracts from 

 beneath the flower. Could you kindly send us a more perfect 

 e.xample ? then we could name it with certainty. 



JNI. J. W. — We have not received any sea-weeds from you. 

 If you have others, please to send them. We are constantly losing 

 specimens which have been sent, through correspondents pack- 

 ing them in paper boxes, or match-boxes, or some other similar 

 substances. Not only so, but these frail protections have the 

 stamp placed on them, instead of on a label, the result being 

 a smash the first time the Post-office clerk operates on them. 

 Glass microscopic slides for naming are even foolishly put in 

 envelopes ! An editor soon becomes acquainted with practical 

 physics ! 



Important to Exchangers. — In one of those moods which 

 only Postmasters-General indulge, it has been ordered that all 

 letters addressed with initials only will be returned to the 

 senders after October ist, 1877. We sincerely hope the safety 

 of the British empire is not endangered by correspondents of 

 Science-Gossip, who desire to e.xchange one species of butter- 

 fly for another ! 



J. M. (Huddersfield). — From what we can make of your 

 drawings, there is no doubt one is one of the genera of Star- 

 fishes called AsterophytoK ; the other drawing is that of a genus 

 of sponges called Halichondria. 



