jVor. 25, 1S80] 



NATURE 



91 



Comparison of Abnormal Barometric Movements at Different 

 Stations. — The general resemblance of all Ihese curves to each 

 other is very remarkable ; indeed if the Mauritius cun-e for 

 the years 1867 and 1S68 be excluded, there is scarcely a single 

 prominent feature in any one of the curves which is not 

 reproduced in the others. To show this the corresponding points 

 of the different curves have been marked with the same small 

 letters. It will be seen, however, that there is strong evidence 

 of a want of exact simultaneity in the barometric movements at 

 different stations, and that as a rule the changes take place at the 

 more westerly stations several months earlier than at the more 

 eastei ly ones. This is particularly noticeable in the curves for 

 St. Helena and Madras from 1S41 to 1846, when the latter some- 

 times lagged behind the former by as mucli as .six months ; in 

 those for Mauritius and Calcutta from 1855 to 1866, when the 

 latter persistently lagged feveral months behind the former ; in 

 those for Bombay and Calcutta from 1862 to 1S66, when the 

 difference in time often amounted to upwards of six months ; in 

 those for Bombay and Batavia from 1S67 to 1878, when (as 

 already remarked) the latter lagged behind the former at an 

 average interval of about one month ; and in tliose for Bombay 

 and Ti-ka-wei from 1876 to 1S78, when the latter lagged up- 

 wards of six months behind the former. It appears then that 

 these long atmospheric waves (if such they may lie called) travel at 

 n very slow and variable rate round the earth from west to east, 

 like the cyclones of the extra tropical latitudes. 



Bombay Fred. Chambers 



(To be continued, ) 



DR. SI EM ENS' S NEW CURE FOR SMOKE 

 T7 ROM among a number of letters which have been sent us on 

 ■*■ this subject we have selected the following for publication ; 

 to these Dr. Siemens has been good enough to append some 

 important remarks. 



In Nature, vol. xxiii. p. 25, I read with interest an article 

 by Dr. Siemens describing an ingenious gas and coke fire which 

 he suggests as a cure for the smoke nuisance. But although the 

 darkening of the atmosphere or fog will certainly be prevented 

 by its use, I am afraid the gases from the coke, especially the 

 carbonic oxide, will make the fogs at least as poisonous and 

 injurious to health as the open coal fires at present in use. 



In these circumstances a description of an " Asbestos gas fire " 

 free from this objection, which we have had in use in our 

 smoking room for the last three years, and which, after a few 

 alterations, has proved perfectly satisfactory, may perhaps interest 

 your readers. 



A :|-inch gas-pipe furnishtd with four Bunsen burners is laid 

 on the hearthstone under the grate and parallel to the ribs, so 

 arranged that the tops of the burners (which are made elliptical 

 to pass through the bars) are flush with the upper surface of the 

 grate, and two inches back from tlie line of the rilis. The fire- 

 place is loosely filled with a preparation of asbestos in pieces 

 about the size of a hen's egg. 



This fire not only evolves a large amount of heat, but has a 

 very cheerful appearance, similar to that of a bright coke fire, 

 and to insure this it is essential that the burners should be 

 placed close to the ribs, as stated above, and not in the centre of 

 the grate. If this is not attended to the asbestos in the centre of 

 the jire will be raised to a high temperature, but will not be 

 sufficient to heat those portions in front, which uill then not only 

 be of no use as radiators in themselves, but act as screens to the 

 light and heat generated in the centre. I suspect this was the 

 cau*e of the failure of Dr. Siemens' pumice gas fire. 



The cost of maintaining ihis fire is simply that of the amount 

 of gas burned, as the asbestos is not consumed, and its prime 

 cost is trifling. I have only further to add that there is not the 

 slightest trace of fumes or smell from the fire two minutes after 

 it is lighted. D. A. Stevenson 



Edinburgh, November 15 



Dr. Siemens has described in your pages the fonn of coke- 

 gas grate which he has fitted in his own house. As I had fitted 

 a similar arrangement in this house before Dr. Siemens' letter 

 appeared in the Times of November 3, and as it is simpler than 

 Dr. Siemens' and succeeds even beyond my expectation, I send 

 you a drawing and description of it. It varies, of course, accord- 

 ing to the shape of the grate in which it is fitted ; but for the sake 

 of comparison I have copied Dr. Siemens' grate, and drawn my 

 arrangement as fitted into it. . 



Instead of Dr. Siemens' arrangement for withdrawing the heat 

 from the back of the fire and bringing it to the front, I merely 

 line the whole grate — sides, back, and bottom— with fire-bricks. 

 This obviates the necessity for the close-fitting ash-pan described 

 by Dr. Siemens, which would be rather expensive to fit. I make 

 the fire-brick in the bottom of the grate slope to\^'ards the front, 

 and leave a space of one inch between the front of it and the 

 perforated gaspipe down which space the ashes fall on to the 

 hearth. 



If my grate is not quite so economical in working as Dr. 

 Siemens', it is very near it, and the first cost of fitting is consi- 

 derably less. In fact, as most grates are lined with fire-brick 

 at back and sides, nothing has to be done but fit a wedge shaped 

 fire-brick into the bottom, a half-inch iron gaspipe, perforated 

 with holes in front, and connect it with the gas service, all of 

 which can generally be done for a few shillings. 



The saving of kindling-wood and of chimney-sweeping would 

 pay for it in a year. In Dr. Siemens' grate the copper must 

 cost about i/. A grate fitted with this arrangement looks exactly 

 the same as an ordinary grate, and there is nothing to prevent 

 ordinary coal being burnt in it — in fact coal can be burnt in it 

 with much less smoke tlian in an ordinary grate by turning on 

 the gas for a few minutes when fresh coal is put on, when the 

 dense black smoke emitted by the new coal is completely burnt 

 up in the gas-flame. To people who object that a gas grate 

 must produce a bad smell in the room I can only say, "Come 

 and see." They will find that we have three grates with this 

 arrangement in constant use in these chambers, and that they 

 produce no smell and make a very pleasant fire. Any person 

 who takes an interest in the subject is quite welcome to come in 

 and look at them at any time. CosMO Innes 



Adelphi Chambers, 7, John Street, Adelphi 



Having been experimenting for some years in the direction 

 referred to by Dr. Siemens in Nature, vol. xxiii. p. 25, I must 

 beg to differ with him most seriously in some of his conclu-ions. 

 The gas-fire with coke which he describes has, so far as our ex- 

 perience goes, several practical objections which prevent its use 

 in the place of an ordinary gas fire, whilst when compared n ith 

 a. good coal fire it fails seriously. 



First, with regard to the objections to Dr. Siemens' fire. It 

 requires about half an hour to become anything like warm, as 

 ai^ainst ten to fifteen minutes with a well-lighted coal fire. 

 Second, it makes as much or more dust and dirt thitn a good coal 

 fire. Third, the grate requires as much cleaning and care as 

 with co-tl. 



I am not surprised at the economy, comparing the coal fire as 

 shown with gas and coke, but if the result had been taken in 



