July 26, 1883] 



NATURE 



299 



Maxwell indeed suggested ("Electricity," vol. i. p. 56) that a 

 layer of extra dense air equivalent to an extra layer of ordinary air 

 about i/2COth inch thick surrounding solids would account for Sir 

 Win. Thomson's remarkable acd puzzling results ; and this is a 

 dimension of the same order of magnitude as the thickness of 

 the dust-free coat on bodies at an ordinary temperature. I by 

 no means intend to imply that the dust-free layer is not com- 

 posed of extra dense air— I have no evidence on the subject- 

 but the dua-freeness may possibly account for its greater 

 strength without the hypothesis of extra density. 



The dustfreeness itself remains to be accounted for. Num- 

 berless experiments suggest themselves. We have not yet tried 

 other gases even, though that is an obvious thing to do. 



It struck me some time ago that the motes in a sunbeam 

 would be convenient weightless bodies for many purposes, to ex- 

 hibit statical lines of force for instance, but the particles of the 

 smoke we have hitherto used have not been sufficiently elon- 

 gated for this purpose. But I anticipate that the examination 

 of all kinds of electrical phenomena in the strongest possible 

 light, instead of in the dark as usual, may lead to various fresh 

 observations. 



The rapidity with which an electrified point clears the box of 

 smoke is so noticeable as to suggest several practical ideas It 

 is somewhat surprising considering the perfection to which 

 electrostatic machines hive been brought that they have not 

 yet received any practical application. The electrical clearing of 

 the air of smoke-rooms, or of tunnels, is perhaps not an imprac- 

 ticable notion. The close relation-hip between fogs, epidemics, 

 &c, and the suspension of solid particles in the air, suggests 

 the use of electrical means for sanitation, and for weatherMm- 

 provement. It has long been known that lightning clears the 

 air, and though ozone may be credited with a portion of the 

 beneficial influence, I fancy the sudden driving away of all solid 

 particles and nuclei must have a great deal to do with it. 



If the germs driven out of the air are condensed on the earth's 

 surface, a partial explanation is suggested of the way in which 

 " thunder turns milk sour," a fact which has always puzzled me, 

 and which appears to be well established. 



I cannot help thinking that the human race will ultimately 

 acquire some means of artificially affecting the weather in a less 

 injurious manner than that which they have hitherto attempted 

 with only too great success, namely, the manufacture of solid nuclei 

 in prodigious numbers for moisture to condense round, and of oily 

 matter to cover the surface of such moisture with, in or ler to 

 prevent its evaporation. As soon as this artificial pollution of 

 the atmosphere has been decisively checked, it will be time to 

 consider whether it may not be possible to keep off even natural 

 mists and rain when they are not wanted, and to assume some 

 sort of control over the weather at critical seasons, instead of 

 halting between superstitious appeals to Providence on the one 

 hand, and a helpless resignation to fate on the other, which are 

 our attitudes at present. 



Meanwhile is it not possible that a periodic optical examina- 

 tion of the atmosphere by a strong beam of light might convey 

 useful meteorological information? Ol iver J. Lodge 



University College, Liverpool, July 1 1 



Antihelios 

 By means of a current of air passed through an ice closet or a 

 closet otherwise reduced in temperature the air of living-rooms 

 might be gauged to any temperature, but say 60° or 70° F. if we 

 pleased. If the air were driven through a preliminary water 

 chamber arranged on the principle of the hubble-bubble pipe, 

 mosquitoes and other flying pests would be excluded absolutely. 

 Imagine the comfort of sitting down to a meal whereat one's 

 food should not be hidden by flying vermin, of reposing in a 

 cool chamber wherein these intruders should be excluded°abso- 

 lutely. When I lay ill of fever in West Africa the atmosphere 

 about me felt simply like the blast from a furnace. What an 

 element of recovery, of possible health and physical wellb.-ing, 

 would it not prove in hospitals when poor fellows 'anguishing m 

 disease should be surrounded by pure, cool, insectless air instead 

 of air at a hundred degrees or even higher. People— some 

 people— say doctors do not feel, but I say that a doctor's heart 

 is rent with anguish when he enters a chamber wherein the air 

 is pestilential, where the sores of wounded men are maggot- 

 infested and the men themselves are eaten up with vermin. ° All 

 this cooler air would prevent or tend to prevent. The festive 

 hall, the school-room, the living-room, the barrack, the church, 



would all experience, the occupants regarded, commensurate 

 relief. It would be just as available in ships as on shore. The 

 Red Sea transit and the blazing oceans of the tropics need no 

 longer be things of terror. In steamships a small percentage of 

 steam power would suffice for driving the cool air current. 

 Wind, water, hand, and steam power could also be rendered 

 available. The vans employed to supply blast-furnaces should 

 suffice for anything, but there is the winnowing van which horse 

 or mule, indeed any animal, could work. Even the simple cir- 

 cular bellows would keep an apartment cool. In towns or in a 

 contonment, a stationary engine with air-ducts leading to the dif- 

 ferent dwellings would satisfactorily replace apparatus adjusted 

 to each separate hous ■. Henry MacCormac 



Belfast, July 21 



Disease of Potatoes 

 ^ The paragraph in Nature, vol. xxviii. p. 281, regarding a 

 "hitherto unknown" diease of potatoes near Stavanger, appears 

 to be identical in everyway with the disease which destroyed the 

 "champion" potatoes in the West of Ireland in August, 1880, 

 described and illustrated by me in the Gardener's Chronicle 

 for August 28, 1880. The bodies de-cribed by Herr Anda, 

 as about the size of a small black bean, are Sclerotia, 

 or masses of highly condensed mycelium, and they have 

 nothing to do with the potato fungus proper, Peronospora 

 infeslans. 



It is a remarkable. fact that neither horticulturists or botanists 

 had ever noticed these large black Sclerotia in rotatoes in Britain 

 before 18S0, and as far as I know no one has ever seen them 

 since. There was a prodigious and destructive growth in 1880, 

 and several botanists as well as myself tried to make the Sclerotia 

 germinate, but a failure resulted in every instance. It appears 

 that Herr Anda has seen the Sclerotia germinating; it is there- 

 fore to be regretted that he has not identified, or got some one 

 else to identify, the perfect fungus. 



WOR'I HINGTON G SMITH 



"Waking Impressions" 



I have before me now a record, written the following morn- 

 ing, of a waking impre-sion of the same order as that told by 

 Mrs. Maclear in Nature, vol. xxviii. p. 270, but which I think 

 shows more clearly the sort of duplexiiy of brain action that one 

 sometimes detects in dreams. 



I awoke with a clear vision of a pamphlet I was holding. 

 The subject was cookery, and about fiur-fifths of the cover was 

 occupied by an engraving of pots and pans, trussed chickens, 

 and other culinary matters. Below this, in one line, printed in 

 capitals all of the same size, was the title which I was reading at 

 the moment of awaking, " FOOD, OR THE ASTROLOGY 

 OF EVERY DAY." 



My first waking impres ion was of the utter irrelevance of the 

 alternative title; but on locking at it with closed eyes moie 

 carefully I saw that the paper in one place had been rubbed, and 

 that a little bit was curled up, leaving a wider srace between 

 " the " and " astrology " than between the other words. The 

 conviction then came to me that a letter was mis-ing, and that 

 the word in full must have been " Gastrology." This of course 

 made sense of the title ; but it is curi us that one's waking in- 

 telligence should be needed to interpret the inventions of one's 

 dreams. E. Hubbard 



I, Ladbroke Terrace, July 21 



A Remarkable Form of Cloud 



While preparing to observe the moon on Sunday, the 22nd 

 inst., at ioh. 20jj. p.m., my attention was attracted to a peculiar 

 patch of grayish white light a few degrees from the moon, which 

 upon closer examination I found extended 1 ight across the 

 heavens, from the north-north-west to the south-south-east point 

 of the horizon, passing throug 1 the zenith. It had a breadth of 

 about 2 3 , and was sharply defined on both sides, more especially 

 the northern, excepting near the zenith, where it was broken up 

 into three or four detached cloudlike masses. All other parts of 

 the sky were perfectly free from clouds, so that this one appeared 

 like a gigantic arch spanning the heavens ; so much so that a 

 person to whom I pointed it outcompartd it to a rainbow, which 

 it very much resembled in form. At ioh. 45m. it was reduced 

 about one-half in width and had shifted 20' from the zenith 



