March io, 1910] 



NATURE 



45 



of the earth's radius, an approximate solution is obtained 

 in the first place neglecting, and in the second place 

 taking account of, the earth's rotation. The author 

 establishes an agreement at least of a qualitative character 

 between the results of his theory and observed facts. 



The Electrician for February ii contains a description, 

 by Mr. P. A. Mossay, of a new arc-lamp known as the 

 Timar-Dreger, which almost dispenses with mechanism 

 and, seems . incapable of getting out of order. The two 

 carbons are placed horizontally, the f>ositive a. few milli- 

 - metres- above the negative, and the arc forms and remains 

 at the ends. To compensate for the want of symmetry 

 of the light, a second pair of carbons is provided which 

 point in the opposite direction to the first. Another new 

 piece of apparatus of interest to illuminating engineers is 

 the Lowden rotary mercury pump, described in the Elec- 

 trical Engineer of the same date. The pump is not unlike 

 the Gaede in general principle, and is much quicker in 

 action than the pumps now used in evacuating incandescent 

 lamps down to pressures at which blackening of the bulb 

 is inappreciable. 



Five years ago the geophysics laboratory of the Carnegie 

 Institution of Washington commenced the task of re- 

 determining, on the constant-volume nitrogen scale of 

 temperature, the melting points of the metals from zinc 

 to palladium. The work has now been completed, and the 

 results are given by Messrs. Day and Sosman in the 

 February number of the American Journal of Science. A 

 platinum-rhodium thermometer bulb has been substituted 

 for the one of platinum-iridium used in the earlier measure- 

 ments, and the bulb has been surrounded by an atmosphere 

 of nitrogen at about the same pressure as that in the 

 bulb to prevent diffusion of the gas through the walls of 

 the bulb. Greater uniformity of temperature throughout 

 the furnace in the neighbourhood of the bulb has been 

 . secured, as the authors consider that this is the chief 

 outstanding error in the use of the thermometer. By 

 means of thermo-couples of platinum plattoum-rhodium 

 standardised by comparison with the nitrogen thermometer 

 they find the following values of the melting points, which 

 may be compared with those of Messrs. W'aider and 

 Burgess, of the Bureau of Standards, given in these 

 columns on February 17 : — cadmium, 3200° ; zinc, 418-2° ; 



■ antimony, 6292° ; aluminium, 658-0° ; silver, 960-0° ; gold, 

 1062-4° ; copper, 1082-6° ; nickel, 1452-3° ; cobalt, 1489-8° ; 

 palladium, 1549-2°. 



The first instalment of an article on the stability of 

 flying machines', by Prof. Herbert Chatley, appears in 

 Engineering for March 4. The author proceeds to inquire 

 under what conditions such machines may be automatic- 

 ally stable ; up to the present, only two types possessing 



■ this quality seem to have been discovered, viz. the auto- 



• matic single-surface glider and the balanced glider. The 

 first relies for its longitudinal stability on the variation of 



• the centre of pressure with the angle of attack ; the second 

 relies on the variation in altitude of a balancer or tail 

 surface. In each case a torque should come into exist- 

 ence which will bring the glider back to its original posi- 

 tion. The author works out both cases mathematically, 



_ and points out for the first case that it is not only ^(/3), 



• the distance of the centre of gravity ahead of the centre 

 of area of the plane expressed as a function of the angle 

 of attack jB, which decides the stabilit}', but the rate of 



' change of the torque M produced by a small alteration in 



)8 owing to a change in the velocity. There seems no 



. doubt that surfaces which are concave on the under side 



J are not stable without some balancing device. The ques- 



•tion of oscillations is also discussed in this article. 



XO. 2106, VOL. 83] 



Bulletin No. 34, issued by the Engineering Experiment 

 -Station of the University of Illinois, contains an account 

 of tests on a water-tube boiler having two types of tile- 

 roof furnaces. The tests were conducted by Mr. J. M. 

 Snodgrass, and in the first four the tubes of the lower row 

 were completely surrounded by the tiles which formed the 

 roof of the furnace ; in the other four tests the under sides 

 of the tubes were exposed to the action of the furnace 

 gases, the roof tiles resting on the tops of the tubes. The 

 last four tests show a slightly higher efficiency, more 

 uniform fire control, and a lower temperature in the 

 furnace, combustion chamber, and stack as compared with 

 the first four tests. The covered tubes were shown to be 

 superior in the matter of smokelessness. About 5 per 

 cent, more water per pound of coal was evaporated with 

 the exposed tubes, and the temperatures in the furnace 

 and combustion chamber were found to be from 200° to 

 400° F. less with these tubes than with those wholly 

 covered. Copies of the bulletin may be had gratis from 

 \V. F. M. Goss, University of Illinois, Urbana, Illinois. 



Messrs. Macmillan and Co., Ltd., have published the 

 first part of a " Key to Hall and Stevens's School Arith- 

 metic," prepared by Mr. L. W. Grenville. The price of 

 this part is 4s. 6d. 



The Amateur Photographer of March 8 is a special 

 issue, containing a number of fine reproductions of 

 photographs, printed in two colours on art paper, as well 

 as valuable notes on scientific and artistic aspects of photo- 

 graphy. The price of this issue is only twopence, notwith- 

 standing these special characteristics. 



A POPULAR edition of the " Naturalist on the River 

 Amazons," by the late Henry Walter Bates, F.R.S., has 

 been published by Mr. John Murray at the price of is. 

 net. We welcome the publication in cheap form of 

 standard books of travel of this kind as being likely to 

 interest the general reader in the work of scientific 

 naturalists and explorers. 



OUR ASTRONOMICAL COLUMN. 



Brilliant Fireball of February 27. — Mr. W. F. 

 Denning writes : — " On February 27, at 6.55, a magnifi- 

 cent meteor was observed at various places. It fell slowly, 

 and illuminated objects around like the bright Tjall of a 

 Roman candle. The meteor is remarkable in two respects, 

 namely, for its unusual proximity to the earth af the end 

 of its career and for the intense green colour exhibited 

 by its nucleus as it sailed down the sky. Several in- 

 dependent observers say the object apparently reached the 

 horizon, or got within 2° or 3° of it, before it became 

 extinct. Its height was certainly not more than twelv^ 

 miles at the end of its luminous career, which occurred 

 over a point about twenty miles west of the island of 

 Anglesey. Possibly, indeed, the meteor may have fallen 

 in the Irish Channel, but evidence must be awaited from 

 places nearer the scene of the event than any we now 

 possess. 



" The radiant point seems to have been in the N. region 

 of Cancer, and this is a place from which several I.irgp 

 fireballs have been directed in past years at the end of 

 February and early in March. 



" There is gocKi reason to suppose that the meteor 

 penetrated our air strata so far as to arrive in a compact 

 form and still luminous to within seven or eight mil'^s of 

 the earth's surface, but more exact observations can alone 

 enable trustworthy figures to be deduced." 



Comet 1910a. — Further light is thrown on the time and 

 circumstances of the discovery of comet 1910a by Mr. 

 Innes in a communication published in No. 4389 of the 

 .4stronomische Nachrichten, p. 338, 



