2^6 



NA TURE 



[July 12, 1894 



Renan having installed in front of the eyepiece a prism which 

 reversed the direction of apparent movement of the stars, either' 

 in right ascension or declination. 



The "Supplement a I'Histoire Celeste de Lalande" is 

 undergoing revision, and the positions of 2250 stars are re- 

 quired to be re-observed, each three times by meridian 

 observ-ations. Since April 1S93, sixty series, comprising about 

 1000 stats of the catalogue, have been obtained. 



The risiiin; of the meridian observations made during the 

 year shows that the instruments were by no means idle, no less 

 than 17,248 observations having been made. The resume of the 

 planets observed during the same period gives the total number 

 as 556. 



Equatonaux CouJis. — The large equatorial has been re- 

 ceiving several alterations and additions, and it is hoped to 

 maintain the position of a fixed or movable star on the same 

 part of a photographic plate with an approximation of o ""2 nearly. 

 The small coudc has been the means of eft'ecting the complete 

 measurements of 1S6 double stats, besides some observations of 

 minor planets, comets, occutlations, &c. 



The Equatoiial in the West Touer. — This instrument is under 

 the direction of M. Bigourdan, who, with M. Faye, were away 

 observing the total eclipse of the sun at Senegal. During their 

 slay there, fifteen lunar culminations for longitude and four series 

 of obser\-ations for latitude were made, besides meteorological 

 observations and four independent determinations of the rela- 

 tive intensity of gravity. The ■■olar observations, among other 

 things, consi>ted in observing the four contacts, and searching 

 round the limb of the sun for any small bodies that might be 

 visible. 



The observations made with the equatorial above referred to 

 consisted of measurements of 2S0 double stars, besides those of 

 comets, occultations, &c. 



The equatorial in the cast tower, under M. Callandreau's 

 direction, has been devoted chiefly to observations of minor 

 planets. 



In the departments where photography is employed, MM. 

 Henry have obtained, among other results, 169 cliches for the 

 catalogue of the Carte an Ctel, twenty-nine large cliches of the 

 moon, enlarged directly eighteen times, these latter marking 

 " un progres ties sensible sur les resultats obtenus anterieure- 

 ment." 



The "Bureau des Mesures des Cliches du Catalogue," under 

 Mdlle. Klumpke's supervision, is now supplied with two 

 machines. The total number of stars measured in the twelve 

 months amount to 27,750 ; of these 26,831 were measures of 

 stars, 343 measures of double stars, and 32 planetary measures. 



The meteorological observations and the hour service have 

 been regularly continued, the latter without any failure during 

 the entire year. 



In the >pectrosc9pic department, M. Deslandres has been 

 continuing the researches on the sun and stars ; but much time 

 was devoted to the preparations for the observations of the total 

 eclipse of the sun last >car. The results obtained during the 

 eclipse consisted of twenty-two photographs of the corona. Some 

 of the negatives show luminous jels from the corona extending to 

 a distance of two diameters. The ultra-violet spectrum of the 

 corona has been traced up to the limit of the ordinary solar 

 spectrum, and in addition fifteen lines have been observed in 

 the new region. In the researches concerning the rotation of 

 the corona, it has been found that one of the negatives shows 

 the spectra of two points of the corona, situated at the ex- 

 tremity of an equatorial diameter and 10' from the solar limb, 

 placed side by side. The bright H and K lines of calcium 

 present a slight displacement corresponding to a ditVercnce of 

 velocity of 5 to 7'5 kilometres. M. Deslandres admits 

 that the solar corona is animated with a motion of rotation, 

 the angular velocity of which corresponds with that of the sun. 



Other spectroscopic work being continued is that of the study 

 of the ralial vclociiics of prominences and stais. 



rj/E CHEMISTRY OF CLEANING.^ 



/\ S a great city grows, and the agglomeration of struggling 



humanity increases, such questions as the dispotal of 



tewagc and other waste matter rise from comparative insignifi- 



gance into problems of almost insurmountable difhculty ; and 



' A lecture Mtitt'.'i ai ihc LoniJon Inililulion, by Prof. Vivian L«wes. 



MO. 1289, VOL. 50] 



whilst we are able to put the burden of cleansing our towns 

 upon the urban authorities, the responsibility of keeping our 

 homes and bodies in a condition of at least sanitary cleanliness 

 devolves upon the individual, and a knowledge of the causes of 

 dirt and the methods by which it can be removed, cannot be 

 regaided as devoid of interest, or at any rate utility. 



Before we can cleanse, we must have dirt to remove, .ind this 

 prime factor of our subject naturally must claim our first 

 attention. 



Dirt has been variously defined : a great statesman has 

 spoken of it as " matter out of place," poets have christened it 

 the "bloom of ages," whilst more niaiier-offact individuals 

 have been content 10 look upon it as something which causes 

 an infinite amount of trouble in the household, and leads to the 

 consumption of much soap and water. If, however, we divest 

 our mind of prejudice, and approach the subject of dirt from 

 a scientific point of view, we shall find a silver lining to the 

 grimy cloud, and shall have to admit that a wondrous store of 

 interest is to be found in the dust with which the housemaid 

 wages perpetual war, and which when glued by nature to our 

 skins, requires special methods for its removal. 



Observ.-ition shows that in our town houses, only a very short 

 interval of time is needed to cause a considerable deposit of dust 

 upon any horizontal surface, whilst vertical surfaces and 

 draperies, especially if their surface be rough, also accumulate 

 a considerable quantity, although of a lighter and more finely 

 divided kind. We also find that this dust is borne to its resting 

 place by the air which penetrates from the outer atmosphere, 

 and that its deposition is caused by the comparative con- 

 dition of rest insured to it by the absence of wind or violent 

 currents. 



The presence of these air-borne particles of solid matter can- 

 be made visible in any town by allowing a beam of sunlight or a 

 ray from an electric lantern to pass through the air of a dark- 

 ened room. If the room be filled with air previously filtered by 

 passing it through cotton wool, the beam of light is invisible 

 until it strikes the opposite wall ; but if the air he unliltered, the 

 path of the beam is mapped out by the suspended matter re- 

 flecting and dispersing portions of it, and so becoming visible to 

 the eye as " the motes in the sunbeam." 



The heavier the nature of the particles, the more quickly will 

 they settle, with the result that the dust on horizontal surlaces, 

 such as the tops of sideboard, piano, and mantel-board, may be 

 expected to differ somewhat from the lighter form, which has 

 continued to float until contact with vertical surfaces has brought 

 it to rest. 



These particles of dust arc composed of matters of the most 

 varied nature, and will be found, when collected, to consist 

 partly of mineral and partly of organic substances, namely, 

 siliceous and carbonaceous matters, hair, epidermis from the 

 skin, pieces of vegetable fibre, pollen from various plants and 

 grasses, the sporidix of fungi and bacteria. 



The heavier portions of the dust are found to contain ground- 

 up siliceous matter, pulverised by traffic in the road ; small 

 particles of salt carried inland by winds from the sea, together 

 with sulphate of soda, with other impurities of a local chai.icter. 

 If a sample of dust be collected and carefully ignited, the organic 

 matter will be burnt away, and any ammonium salts volatilised, 

 whilst the mineral portion will be unacted upon ; and in this 

 way it has been shown that nioreth.in one hall of the suspended 

 matters in the air arc of organic origin, a large portion of this 

 organic matter consisting of germs which are capable of selling 

 up fermentation, disease, and decay. 



It is only within the last few years that the importance of the 

 work done by the solid particles of dust floating in the air has 

 been recognised, and it is to Pasteur that we owe the know- 

 ledge that these germs set up the various processes of organic 

 decay. 



Pasteur collected the lightest portions of dust, which arc left 

 floating in the air after the heavier portions have settled down, 

 by gently drawing air through a plug of soluble collodion cotton ; 

 and after he had collected sufficient dust in this w.ay, he di^ 

 solved the cotton in a mixture of alcohol and ether, and ex 

 amining the residual p.articlcs under the microscope, was able 

 to show the presence of a large and variable number of organisms 

 obtained from the atmosphere. 



lie also found that solutions of sugar mixed with beer yeast, 

 and left exposed to Ihc air, rapidly decomposed. If, however, 

 the solution was kept in contact with air, that had been pre- 

 viously healed, it would remain unchanged for months, but de- 



