356 



NATURE 



{Feb. 7, 1889 



account of ultramarine is given as follows : — " The basis of this 

 colour is Lapis Lazuli. This, added to the long and tedious 

 operation of extracting the Blue, makes this colour very dear. 

 In order to prove the goodness of Lapis LmzuU, make it red hot 

 upon a plate of iron ; and then throw it immediately into strong 

 white Vinegar, If it loses its colour, it is of an inferior quality. 

 You may likewise form a judgement by its weight, the real 

 Ultramarine being much heavier than the false." 



It is stated that the stone comes from Asia, where it is found 

 on the frontiers of Tartary, China, and also from America. 

 Having drawn my conclusions as to the behaviour of ultra- 

 marine with acids, from the preparations sold for this pigment, 

 it seemed desirable that the behaviour of the mineral should be 

 studied by itself, and likewise that of the artificial preparation. 

 This latter, I am aware, is variable ; some of it is more easily de- 

 composed by acids than other samples, the 'difference being 

 occasioned by the greater amount of silica in the latter. 



I applied to Mr. Gregory, of 88 Charlotte Street, Fitzroy 

 Square, for as many different specimens of lapis lazuli and 

 minerals resembling it as were at his disposal. They consisted 

 of a specimen from Chili, two from Persia of magnificent colour, 

 three from Siberia, Trans-Baikal, and a specimen of a blue 

 mineral often mistaken for lapis lazuli called glaucolite. This 

 also occurs in the Trans-Baikal district. 



These specimens were chipped, where fragments of a fine blue 

 colour were to be seen, and the pieces were ground in an agate 

 mortar to an impalpable powder. 



A specimen of each was placed in the hollow of a white 

 earthenware colour palette, and moistened with sulphurous acid. 

 All the specimens of lapis lazuli were attacked, and in nearly 

 every case completely decolorized. Where the blue colour was 

 not quite destroyed, the powder was examined with a powerful 

 lens, and it was seen that blue particles remained which had not 

 been sufficiently finely powdered. Several minute lumps of the 

 colour were noticed to be etched by the acid, showing white 

 spots here and there. Hence the fineness of the powder has 

 much influence on the facility with which the mineral is attacked. 

 This is usual with all mineral substances. 



It was next considered of interest to ascertain whether lapis 

 lazuli will stand the test applied to it by Constant de Massoul, 

 and therefore some of the powdered mineral was made red-hot 

 and thrown into dilute acetic acid ; after waiting for five minutes, 

 the blue colour was not appreciably diminished, and it is to be 

 presumed that its nature would thus be satisfactorily demonstrated. 

 Under these circumstances, however, the colour is in considerable 

 quantity, and though some of it may be acted on, yet it is not all 

 destroyed, neither is the tint altered. But in the previous expe- 

 riments, the powder was much finer and in a thin layer, and 

 though there was a slight action immediately, yet it was about 

 an hour before the colour was completely destroyed. The speci- 

 mens did not all behave exactly in the same way : some were 

 destroyed more readily than others, especially those from Chili 

 and from Persia. 



It does not appear, therefore, that my statement concerning 

 the use of ultramarine as a pigment upon drawing-paper requires 

 modification. A wash of bluish-gray, obtained by mixing light 

 red with ultramarine, was handed round at the Birmingham 

 meeting, one-half of which was shown to be of a foxy red tint 

 after treatment with sulphurous acid. This is, of course, beside 

 the question as to whether ultramarine is largely used for gray 

 tints in the form of water-colour by artists. 



Touching the mineral glaucolite, its composition, according to 

 the analysis of G. von Rath, quoted in Dana'ws " Mineralogy," 

 is the following : silica 47*49, alumina 27*57, ferric oxide i"54, 

 magnesia o*47, lime I7'i6, soda 471, potash 0-58, and water 

 0*48 per cent. It is quite unacted upon by the acids which 

 decompose lapis lazuli. It is highly improbable that it has 

 ever been used as a pigment, because in the form of powder 

 its colour is poor. W. N. Hartley. 



LONDON ANCIENT AND MODERN, FROM A 

 SANITARY POINT OF VIEW> 



T^R. POO RE began by reminding his hearers that the mere 

 ^-^ age of London was one of the reasons why it became un- 

 wholesome. Roman London was buried deeply amongst rubbish 

 of all kinds, much of which was putrescible, and, therefore, a 

 source of danger in the soil. 



* Abstract of a Lecture delivered by Dr. G. V. Poore at the Sanitary 

 Institute on Thursday, January 24. 



Ancient London was well placed and magnificently supplied 

 with water, for in addition to the Thames there were many 

 streams, such as Westbourne, Tybourne, the Fleet River, 

 Walbrook, and Langbourne, which originally were sources of 

 pure water. All these brooks, however, had become disgrace- 

 fully fouled, and for very shame had been covered over. One 

 great drawback to the site of London was the proximity of 

 marshy land on every side except the north-west, and formerly 

 from this cause malarial fever and dysentery were great causes of 

 the high death-rate. 



In medireval London, and even down to the eighteenth cen- 

 tury, the houses were not so closely packed as they are now. 

 Reference to Aggas's map (time of Elizabeth) would show that 

 there was a great deal 'of garden ground within the City, and 

 on comparing this map with Newcourt's map (Charles II,) it 

 was evident that just before the Plague and the Fire the crowding 

 of houses had become very much greater than it was in the time 

 of the Tudor monarchs, who discouraged building near or in 

 London. 



Parker's map (1720) would also show that after the Fire the 

 houses were not so closely packed as in the days of the Stuarts, 

 for in this map a surprising amount of garden ground is visible 

 within the walls. At this time also Moorfields was not built 

 upon, and remained as a playground and air space as it had done 

 for centuries previously. That mediaeval London was very un- 

 healthy, a perfect fever den, there could be no doubt. The 

 Black Death in 1349, and the Sweating Sickness two centuries 

 later, were times of great mortality which struck the popular 

 mind, but it was not till 1593, when bills of mortality were first 

 introduced, that we began to have any certain knowledge of the 

 amount or the kind of disease prevalent. There was reason to 

 think, however, that in the eighteenth century (after the Fire and 

 the Great Plague) the deaths exceeded the births by about 600,000 

 in the hundred years. 



The fatal diseases were mainly fevers — malarial fever, small- 

 pox, typhus, measles, and (latterly) whooping-cough. The 

 causes of the enormous mortality of mediaeval London were 

 due — (i) To the marshy undrained soil, fouled with refuse of 

 every kind. (2) The filthy state of the unpaved city, and a 

 perfectly swinish condition of the houses of the lower orders. 

 (3) The ill-nourished and drunken condition of the masses, 

 among whom a taint of scurvy was very common. (4) The 

 condition of superstition and brutality (as evidenced by the 

 punishments and the pastimes) which made any measures of 

 public health impracticable. (5) The management of epidemics 

 was bad, with a total neglect to separate the sick from the 

 sound ; and, finally, the medical faculty were scarcely less 

 ignorant and superstitious than their patients. 



Turning to modern London, the lecturer said there had been 

 a great and manifest improvement ; but when we looked at the 

 low figure which is called the London death-rate, several things 

 must be taken into consideration, e.g. (i) The London of the 

 Registrar- General included large districts such as Lewisham, 

 "Wandsworth, Fulham, &c., which, in great part, were scarcely 

 urban in character ; and these being occupied largely by well-to- 

 do persons, lowered the average death-rate for the whole city. 

 (2) London being a city in which wealthy people abounded, its 

 death-rate must not, in fairness, be compared to a city packed 

 with undiluted operatives. (3) The mobility of the population 

 was so great that this fact must vitiate our statistics, and it was 

 to be remembered that nothing quickened the departure of an 

 individual from London more than ill-health. (4) The age 

 distribution in London was very abnormal. It was largely re- 

 cruited by selected adults from the country, and there was a great 

 deficit in the extreme ages among which (the very young and very 

 old) death-rate is always highest. (5) Again, the diminishing 

 birth-rate (that for 1887 was 2 '8 below the average of the pre- 

 vious ten years) very greatly diminished the death-rate in a city 

 where 158 children out of every 1000 born die before they are 

 one year old. 



It was difficult to believe that Londers were very robust when 

 more than 25 per cent, of them had recourse to the public 

 hospitals in the course of the year. 



The cause of the diminished death-rate (which was very con- 

 siderably reduced after every allowance had been made) was due 

 — (l) To the increase of knowledge, not only among doctors, 

 but amongst the people generally, for we must remember that 

 "self-preservation is the first law of Nature." (2) Vaccination, 

 and the modern plan of treating infectious diseases by the prompt 

 separation of the patients, had done a great deal ; the total absence 



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