1823.] Scientific Intelligence* 71 



ful in case of accident to destroy the partition wall betn-een the house 

 and the establishment which contains the steam-engine. 



The commission also proposes that an exact account should be kept 

 by authority of all the accidents which happen to steam-engines of 

 every construction, and to pubhsh this statement, mentioning the 

 causes and effects of such events, the name of the manufacturer of the 

 steam-engine, and this (they observe) is the most efficacious of all 

 methods to prevent the misfortunes which result from the use of steam- 

 engines, whether of low, middling, or high pressure. — (Ann. de Chim.) 



X. On the Phosphates of Lead. By N. J. Winch, Esq. Hon. MGS. 

 (To the Editor of the Annals of Philosophy.) 



SIR, ~ Netvcastle-tijpoH'Tyne^ Jan. 23, 1823. 



From an itinerant dealer, who collects minerals at the lead hills in 

 Scotland, I lately procured a variety of the phosphate of lead, which I 

 suspect is not described in any of our mineralogical arrangements, or 

 scientific journals, ' The ore in question is of as bright and deep an 

 orange- red colour as the chromate of lead, and consists of groups of 

 simple six-sided prismatic crystals, from an eighth to a quarter of an 

 inch in length, filling cavities in pale-yellow crystalline phosphate of 

 lead. The crystals are brittle, possess an adamantine lustre, and are 

 accompanied by grey, white, and lemon-coloured carbonates of lead, 

 together with galena. Placed on charcoal before the reducing flame 

 of the blowpipe, it decrepitates, and immediately becomes nearly 

 black ; then easily fuses into a pale-grey enamel. On borax being- 

 added, it melts with effervescence, and the glass formed is of a yellow- 

 ish milk}'^ hue while cooling, but transparent and colourless when quite 

 cold, with air bubbles and globules of lead dispersed through it. Here 

 it may not be amiss to mention the results obtained by means of the 

 blowpipe by some of the most able writers on mineralogy, on testing 

 this ore. Brongniart, at p. 201, vol. ii. says, " Le plomb phosphate 

 ne fait aucune effervescence dans les acides, et se fond au chalumeau 

 sur le charbon en un globule qui prend un surfiice polyedrique en si 

 figeant. Tl n'est point reductible en plomb sans I'addition d*un peu 

 potasse et de charbon." Berzelius on the Blowpipe, at p. 358, 

 observes, " Phosphate of lead alone on charcoal fuses in the exterior 

 flame ; the globule crystallizes ; and, after cooling, has a dark colour. 

 In the interior flame, it exhales the vapour of lead, the flame assumes a 

 bluish colour, and the globule on cooling forms crystals with broad 

 facets inclining to pearly whiteness. At the moment it crystallizes, a 

 gleam of ignition may be perceived in the globule. With borax, it 

 behaves like oxide of lead." Phillips's account of this process, at 

 p. 256, is as follows : " Before the blowpipe on charcoal, phosphate of 

 lead usually decrepitates; then melts, and on cooling forms a polye- 

 dral globule, the faces of which present concentric polygons. If this 

 globule be pulverized and mixed with borax, and again heated, a milk- 

 white enamel is the first result. On the continuance of the heat, the 

 globule effervesces, and at length becomes perfectly transparent, the 

 lower part of it being studded with metallic lead." In the third edi- 

 tion of Jameson's Mineralogj^, vol, ii. p. 372, the same account is 

 given ; but in the second edition, vol. ii. p. 368, that author observes, 

 " Before the blowpipe, phosphate of lead does not fly into pieces, but; 



