June 19, 1913] 



NATURE 



399 



species recorded sparingly from a few localities, but 

 off Redcar it occasionally appears in extraordinary 

 shoals in springtime. Such visitations have occurred 

 previously in the second week of February, 1892, 

 April, 1907, and April 2, 190S. In general the 

 creatures come ashore after a N. or N.E. wind, 

 but on the present occasion a gentle westerly wind 

 had prevailed for a few days. I should be glad to 

 receive information from naturalists or fishermen 

 who may have observed these minute " shrimps " about 

 the same date, on other parts of the coast or in the 

 open sea, so that knowledge may be gained of the full 

 extent and of the provenance of the shoal. 



James Ritchie. 

 Royal Scottish Museum, Edinburgh. 



New Zealand Vegetation. 



In Nature for April 10 (p. 147), under the title 

 "New Zealand Vegetation," I notice the following 

 sentence : — "The northern rivers and estuaries display 

 a mangrove vegetation — a unique and unexpected 

 occurrence outside of the tropics." 



The writer of the article is evidently not aware that 

 mangrove formations are found at intervals all round 

 the coasts of Australia. The species which forms them 

 is Avicennia officinalis, L., which occurs in all the 

 Australian States, but not in Tasmania. It reaches 

 its southerlv limit in Western Australia in the neigh- 

 bourhood of Bunbury (33+ S.), where the trees reach 

 a height of about 12' ft. On the east coast it is most 

 familiar on the shores of the Parramatta River in 

 Svdney Harbour, which is a little further south than 

 Bunbury, but it occurs so far south as Corner Inlet, 

 on the east side of Wilson's Promontory (39° S.). This 

 southernmost point of the Australian continent is one 

 degree further south than any point on the north 

 coast of the North Island of New Zealand. 



W. B. Alexander. 



The Western Australian Museum and Art Gallery, 

 Perth, Western Australia, May 10. 



phenomenon on dew on seakale, may be of interest. 

 It was taken here on October 7, 1899, at 8.35 a.m. 

 It shows the shadow of the camera, so that in spite 

 of the irregularity of the leaves the radius of the 



I fear that in attempting to compress into a few 

 paragraphs _a general sketch of the plant communities 

 of New Zealand I inadvertently conveyed the 

 erroneous impression concerning the distribution of 

 the mangrove vegetation in Australasia which Mr. 

 W. B. Alexander has corrected in his interesting 

 note. The sentence which he quotes is perhaps less 

 misleading if read in connection with that imme- 

 diately preceding it, and containing the statement 

 upon which I wished to lay chief stress in enumerat- 

 ing the main types of New Zealand vegetation — "to 

 find an equal variety a continent extending to the 

 tropics would have to be visited." I was quite aware 

 of the well-known fact that the eastern or Indo- 

 Malayan mangrove flora, well developed on the 

 northern littoral of Australia, extends in an im- 

 poverished form along the eastern and western coasts 

 southwards, though it is interesting to note that it 

 actually reaches the most southerly point of the Aus- 

 tralian continent. It may be added that Prof. Bews 

 (Annals Natal Museum, ii., 1912, p. 297) has recently 

 described what appears to be the most southerly ex- 

 tension of the mangrove vegetation on the opposite 

 side of the Indian Ocean, in Durban Bav ; here, as 

 in the subtropical and warm temperate parts of Aus- 

 tralasia, the rich eastern mangrove flora is represented 

 by an interesting though poorly developed outlier con- 

 sisting of Avicennia officinalis, Bruguiera gytnno- 

 rhiza, and Rhizophora mucronata. F. C. 



Anthelia. 



In connection with the correspondence in Nature 

 on the bright light on dew round the shadow of one's 

 head, the accompanying photograph, which shows the 

 NO. 2277, VOL. 91] 



bright light is easily measured as nearly 8°. The 

 scale of the photograph is 8-5° to the inch. 



T. W. Backhouse. 

 West Hendon House, Sunderland, June 10. 



Antenna? for Wireless Telegraphy. 



I was interested to see Mr. Campbell Swinton's 

 letter on wireless receiving with his bedstead as an 

 aerial. Many of the more powerful stations are, 

 however, much easier to receive than is generally 

 supposed ; for instance, I have been able to read the 

 Eiffel Tower nine o'clock news message with only 

 12 ft. of No. 18 S.W.G. copper wire stretched across 

 my attic (second floor, about 25 ft. from the ground) 

 using good earth to waterpipes, with usual tuning 

 coils and condensers, bornite-zincite detector, and very 

 sensitive 4000 ohm telephone (H. W. Sullivan), with- 

 out any relay- Even when the aerial was reduced 

 to 6 ft. of wire the signals were just audible, but 

 very faint. Arnold G. Hansard. 



Limpsfield, Surrey, June 10. 



Some months ago, in endeavouring to reduce the 

 antenna to the smallest possible dimensions, such as 

 bv placing a series of wires just over the instruments, 

 I found that by using a bedstead (without wire mat- 

 tress) signals of "strength 8" — i.e. moderately 

 loud — could easily be obtained from Paris without the 

 aid of a Brown relay — a costly instrument, reputed to 

 increase the strength of signals five times. The appa- 

 ratus used was simply the orthodox loose coupling 

 with crystal detector. The bed used is on the second 

 floor of my house, about 20 ft. from the ground, and 

 the gas-pipe below the same floor served as an earth 

 connection. 



Under the same conditions Norddeich is usually 

 readable, and sometimes Poldhu and Nauen. That 

 nearer stations are also heard is obvious. 



I should be pleased to give a demonstration of 



