NA TURE 



[April 6, 1893 



vated. The Rev. Dr. B. C. Henry, in a letter dated January 26, 

 informs me that " the destruction of vegetation about Canton 

 has been very great. The banana plantations are ruined, and 

 the bamboos have suffered. The Aleurites triloba look all 

 shrivelled up, while Begonias, Euphorbias, Crotons and scores 

 of others are simply destroyed." What Dr. Henry reports in- 

 dicates severer weather at Canton than here, Aleurites triloba 

 leaves being shrivelled up at Canton, while they are here at 3CX5 

 feet altitude uninjured, but at 600 feet they are affected, and 

 completely destroyed a little higher up the hill, 



(23) Accompanying this report are six photographic views 

 which were taken on January 16 showing the ice at various 

 places in the Peak district. It is somewhat difficult to represent 

 ice in photographs, as bright light has much the same effect as 

 ice which owes its white appearance merely to reflected light, 

 but it will be understood that the white in these views is pro- 

 duced by ice. Charles Ford, 



Superintendent Botanical and Afforestation Department. 



Hon. G. T. M. O'Brien. C.M.G., 

 Colonial Secretary, &c. 



The importance of such facts as these in connection with geo- 

 graphical distribution can hardly be overrated. It is customary 

 to compare the range of a plant with the corresponding mean 

 annual temperature. But it is obvious that the exterminating 

 effect of occasional low temperature must override every other 

 condition. An island is often the last refuge of a species not 

 found elsewhere. Such a frost as occurred in Hongkong would 

 erase the Double Cocoa-nut in all probability from the face of 

 creation, if it occurred in the Seychelles. In any case islands are 

 not easily restocked except-with littoral vegetations and the trees 

 distributed by carpophagous birds. It seems evident therefore 

 that the geographical distribution of plants may still be influenced 

 by causes which are catastrophic in their nature. Of this, 

 although not from cold, there is already a striking illustration in 

 the simultaneous destruction of the entire forest vegetation 

 which at one time covered the island of Trinidad in the South 

 Atlantic. Mr. Knight, in the account which he has given in 

 the " Cruise of the Falcon," conjectures that the cause was 

 more probably volcanic than a long drought. 



The wave of cold which affected •: Hongkong (or at any rate 

 the atmospheric conditions which produced it) seems to have 

 been tolerably extended in its range. My friend. Dr. Trimen, 

 writes to me on February 6 from Ceylon : — 



" We are having a wonderfully fine and dry time here, with 

 extraordinary cold mornings. Here at Pecadeniya we have 

 been registering at 6 a.m. 53° and 54° F., the lowest ever previ- 

 ously known being a little below 60°. The middle of the day 

 is very hot. Hakgala has been getting frost for the first time on 

 record. " 



He does not give any dates ; but the two exceptional circum- 

 stances are sufficiently near together to make it probable that 

 some common cause produced them both. 



W. T. Thiselton-Dyer. 



Royal Gardens, Kew, March 28. 



P. S.— Since writing the above I have received from the 

 Colonial Office the accompanying report on the weather of 

 January from the Hongkong Observatory. — [W. T. T.-D.] 



The mean temperature was below the average from the 14th 

 to the 24th. The coldest day (air 35° '2, damp bulb 32° -8) was 

 the 16th. The lowest mean temperature of the damp-bulb 

 thermometer occurred on the 17th (air 36°-2, damp bulb 30°*9). 

 Circumstances were anti-cyclonic, with probably abnormally 

 slight decrease of temperature with height. Snow-storms were 

 reported from China to the north and east of the colony. From 

 Macao snow was reported, but that appears to have really con- 

 sisted of small-sized hail, which fell for four hours. Neither 

 snow nor hail were seen in Hongkong, but the tops of the hills 

 appeared to be covered by snow or hoar-frost. Water exposed 

 in buckets or in pools was several mornings found covered with 

 ice about \ inch thick, and a few hundred feet above sea-level 

 both the grass and branches of trees, being cooled below the 

 temperature of the air (which did not fall below freezing-point) 

 owing to evaporation and radiation, were encased in unusually 

 clear and transparent ice without any appearance of crystallisa- 

 tion. As far south as the Straits Settlements the cold was felt,' 

 but in a less degree. The temperature appears not to have fallen 

 below 70° in Singapore. At sea strong northerly breezes were 



NO. 1223, VOL. 47] 



observed during the greatest cold. The colony was sheltered 

 by the mainland, andonly light northerly breezes were registered 

 till the 20th, when the wind backed to west. It veered to 

 east on the 21st. During the coldest days the pressure was from 

 one to two-tenths of an inch of mercury above the mean. The 

 sky was overcast, but cleared on the evening of the 17th. Owing 

 to radiation the extreme temperatures occurred after this epoch : 

 the lowest air-temperature 32°'o about 7 a.m. on the i8tli, and 

 the lowest damp-bulb temperature 27°7 about 2.30 a.m. on the 

 same day, W. Doberck, Director. 



Hongkong Observatory, February i. 



Mr. Preece on Lightning Protection. 



In the recent Presidential Address to the Institution of Elec- 

 trical Engineers by Mr, Preece, I find the following reference 

 to myself. 



"Prof. Oliver Lodge has . . . endeavoured to modify our 

 views as to the behaviour of lightning discharges, and as to the 

 form of protectors, but without much success. His views have 

 not received general acceptance, for they are contrary to fact 

 and to experience." 



I was quite prepared to laugh at this with the rest, but I find 

 that the general and semi- scientific public are apt to take Mr. 

 Preece's little jokes, of which there are many towards the end 

 of this address, as serious and authoritative statements of 

 scientific fact. And it has been represented to me that unless I 

 take some notice of the above, it may be assumed that I wish 

 silently to withdraw from an untenable position without ac- 

 knowledging having made a mistake. 



Indeed, I have already been questioned by a scientific worker 

 as to whether I accepted the above statement as in any sense 

 corresponding to truth. 



My reply is that so far was I from that attitude, that I did 

 not suppose that the statement was either meant or would be 

 taken seriously. 



The broad question of scientific fact is this : — Given an 

 electrostatic charge at high potential, can the potential be 

 reduced to zero most quietly and safely by a good conductor or 

 by a bad one ? 



The old lightning-rod doctrine (or drain-pipe theory) said, by 

 an extravagantly good one. I say, by a reasonably bad one. It 

 you employ too good a conductor the mean square of current is 

 appallingly strong, and all manner of dangerous oscillations 

 are set up ; whereas in a bad conductor the discharge can be more 

 nearly dead-beat. These oscillations have been experimentally 

 and mathematically demonstrated in a great variety of ways, the 

 unexpected and distinct effects they are able to produce have 

 been displayed, and Messrs. Whittaker have published for me 

 a large book about them. 



Some critics have sensibly objected that the book is too big, 

 but I am not aware of any scientific authority who controverts 

 my position. 



If Mr. Preece only means that these views regarding lightning 

 and its dangers are not yet practically accepted by the great 

 British Telegraphic Department, that is, I admit, perfectly true. 



Oliver Lodge. 



The Author of the Word "Eudiometer." 



For some time past I have been endeavouring to find out the 

 originator of the name eudiometer, which is now applied to the 

 measuring tubes used in gas analysis, and possibly the result of 

 the search may be of interest to some of the readers of Nature. 



Naturally my first resort was to text-books and dictionaries, 

 but although the derivation of the word is sometimes given, the 

 name of the author is not stated. 



I had great hopes that the third edition of the " Encyclopedia 

 Britannica," published in 1797, would contain the desired infor- 

 mation, for the article "Eudiometer " must have been written not 

 long after the invention of the instrument, but it merely calls it 

 "an instrument for observing the purity of the atmospherical 

 air." Descriptions of many forms of eudiometer follow. 



The New English Dictionary gives the derivation and the 

 first quotation is "1777. De Magellan {title). Glass apparatus 



for making mineral waters with the description of some new 



Eudiometers " ; another is " 1807. Pepys. Eudiometer \x\ Phil. 



