HARD WICKE'S SCIENCE- G OS SIP. 



95 



few days in autumn. The pied wagtail's song is not 

 always " subdued ;" at times it is so loud and shrill 

 as to recall rather the canary than the robin-red- 

 breast.— C. B. M. 



The Solar Year.- — Your correspondent T. R. 

 Jones has, perhaps, been misled by some inaccurate 

 astronomical treatise, or perhaps by his own too 

 hasty reading. The year of 365 days 6 hours 9 min. 

 9 - 6sec. is called the sidereal year, and denotes the 

 period in which the sun completes his apparent course 

 through the zodiac, measuring his position with 

 respect to the stars. It does not correspond to the 

 solar year, or period elapsing between two vernal 

 equinoxes : because owing to the sun's own motion 

 through space, the position of the vernal equinoctial 

 point is continually changing. The length of the 

 true solar year is, I believe, 365 days 5 hours 48 min. 

 49*7 sec. Leap year, therefore, is so far from failing 

 to cover the whole deficiency in the length of the 

 calendar year, that it covers too much, and a day 

 will be omitted, not inserted, in the year 1900. The 

 omission of the 29th of February in a leap year is 

 made three times in every four centuries. The re- 

 cognition of this necessity was the celebrated Gre- 

 gorian Reform of the Calendar, accepted by England 

 in 1752, the non-adoption of which by the Greek 

 Church accounts for the fact that Russia and Greece 

 are now twelve days behind the rest of Europe. — 

 C. B. Moffat. 



British Orthoptera. — As I contemplate writing 

 a popular handbook on the above, as a companion 

 volume to my "Illustrated Handbook of British 

 Dragonflies," I shall be very glad to communicate 

 with all who are interested in these insects. Local 

 lists and specimens for figuring would be very 

 acceptable. — W. Harcottrt Bath, Ladyiuood, Birnwtg- 

 ham. 



British Dragonflies. — Will readers who are 

 interested in the above kindly supply me with local 

 lists of same, as I am desirous of elucidating their 

 distribution in this country? — W. Harcottrt Bath, 

 Ladywood, Bhininghatn. 



Sea-Eggs. — I have read with much interest Mr. 

 P. L. Simmond's article on " eggs," in your issue of 

 Science-Gossip; but I was disappointed to find 

 that he made no mention of a kind which I find in 

 the sea-pools, and which has long puzzled me. They 

 are pale green jelly, slightly oval, and of the size of a 

 sparrow's egg ; in the centre is a dark green spot. I 

 find them always in a pool lined completely with the 

 common sea-grass, Enteromorpha compressa, and 

 close to low-water mark. The eggs are separate, 

 each anchored firmly to a blade of the grass. I do 

 not know when they first appear, as I only go to .the 

 sea-side in August, but they have always gone by the 

 middle of September. Hitherto my attempts to 

 hatch them have been unsuccessful. I should be 

 very much obliged if any of your correspondents 

 could identify them for me. — F. Beset, 14 Church Hill, 

 Edinburgh. 



Moths and Water. — In the March number of 

 Science-Gossip Mr. Morley asks why moths (es- 

 pecially the ;winter and early spring moths) show 

 such a marked tendency to fly into pools of water, 

 and suggests that they may be attracted by the 

 reflection of the moon. I doubt this explanation. So 

 far as I have observed moths usually drown them- 

 selves on calm evenings, in the early dusk, while 

 there is still a good deal of daylight remaining, and 



they seem to avoid bright moonlight. About fifteen 

 years ago, on a calm evening, I was walking along 

 the Royal Canal (Dublin), and I noticed that there 

 were large numbers of H. velleda drowning in the 

 water, and that other individuals were skimming the 

 surface. I watched these latter, and I saw how they 

 came to drown [themselves ; they flew over the sur- 

 face, from time to time dashing at it, and gene- 

 rally rising again, until ultimately they made too 

 forcible a dash, wetted their wings, and could no 

 longer rise again. Their flight was exactly similar to 

 the flight of moths close to the ceiling of the room, 

 when they have been attracted by light. Careful 

 watching showed me that the probable explanation is 

 in both cases similar ; in one case the moths chase 

 their reflections in the water, in the other case their 

 shadows on the ceiling. An interesting point in 

 natural selection here presents itself. In the case of 

 moths whose habitat was the banks of lakes, etc., 

 such a tendency would lead to a considerable loss of 

 life, and so be detrimental to the species. Accord- 

 ingly, we should expect that the individuals possessing 

 this tendency would be weeded out, until ultimately 

 it would be entirely eliminated. We should, then, 

 expect that the species which habitually live near 

 water would show little or no tendency to drown 

 themselves. How this may be, my own observations 

 are insufficient to decide. I cannot remember having 

 ever noticed specimens of any waterside species 

 drowned in any number. Possibly some of your 

 entomological readers may have made observations 

 bearing on the subject. — j. R. Holt. 



The Chicago Telescope. — It is commonly sup- 

 posed that we cannot get any further information 

 concerning the stars, because we cannot cast any 

 bigger glass lenses. But if we cannot obtain a larger 

 image in this way, cannot we obtain a better-defined 

 one, and cast it on a transparent screen or photograph 

 it ? This done, it might be examined in detail, I 

 suppose, with a lens? — A. H. Swinton. 



" Sillgreen." — I see by last month's Science- 

 Gossip that one of your correspondents complains 

 that he cannot find the word Sillgreen in the " En- 

 cyclopaedic Dictionary. " The form Sillgreen is a very 

 rare one, if indeed it occurs in literature at all. 

 Silgreen your correspondent will find, with a cross 

 reference to Sengreen. He is of course quite correct 

 in supposing the plant referred to to be Sempervivum 

 tectorttm, the common house-leek. If you have not 

 already answered him, may I ask you to be good 

 enough to incorporate the facts given above in your 

 reply. — The Editor. 



Australian Toeacco. — Surely there is some 

 mistake in note on "Australian tobacco," p. 66 of 

 Science-Gossip for March? Tobacco appears as a 

 regular product of Queensland, in " Chambers's En- 

 cyclopedia," W. & A. K. Johnston's " Atlas" etc., 

 and was recently alluded to in the daily press as not 

 very successful further south. — M. E. Fope. 



NOTICES TO CORRESPONDENTS. 



To Correspondents and Exchangers.— As we now 

 publish Science-Gossip earlier than formerly, we cannot un- 

 dertake to insert in the following number any communications 

 which reach us later than the 8th of the previous month. 



To Anonymous Querists.— We must adhere to our rule of 

 not noticing queries which do not bear the writers' names. 



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