B L U 



In the fame way did many of the early writers account 

 for the phenomenon of a bhie ilij ; fuch as Fromondus, 

 Funccius, Otto Guericke, and many others : their opi- 

 nion long prevailed, and has been adopted by fome in more 

 modern times, efpecially by Wolfius and Mufchenbroek. 

 But in the explanation of this phenomenon, fir Ifaac New- 

 ton obferves, that all the vapours, when they begin to con- 

 denfe and coalefce into natural particles, become tirft of fuch 

 a bignefs as to refleft the azure rays, before they can confti- 

 tutc clouds of any other colour. This, therefore, being the 

 firil colour which they begin to reflect, muft be that of the 

 fiaeil and molt tranfparent flties, in which the vapours are 

 not arrived to a groflhefs fufficient to refleft other colours. 



M. Bouguer, without having recocrfe to the vapours 

 diffufed through the atmofphere, in order to account for 

 the reficttion of the blue-m.aking rays, afcribes it to the 

 conftitution of the air itfelf, whereby thefe fainter-coloured 

 rays are incapable of making their way through any confi- 

 derable tract of it. And he accounts for thofe blue (ha- 

 dows, which were firll obferved by M. Bufton in the 

 year 1742, by the aerial colour of the atmofphere, which 

 enlightens thefe fhadows, and in which the blue rays 

 prevail ; whilll the red rays are not rcflefted fo foon, 

 but pafs on to the remoter regions of the atmofphere. The 

 abbe Mazeas, in a Memoir of the fociety in Berlin, for tlie 

 vear 1752, accounts for the phenomenon of blue fhadows by 

 the diminution of light ; having obferved that, of two fha- 

 dows which were caii upon a white wall from an opaque 

 body illuminated by the moon, and by a candle at the fame 

 time, that which was enlightened by the candle was reddifh, 

 and that which v,'as enlightened by the moon was blue. 

 However, the true caufe of this appearance feems to be that 

 afligned by M. Bouguer, which agrees with the folution 

 given of it about the fame time by Mr. Melville. But 

 inflead of attributing the different colours of the clouds, 

 as fir Ifaac Newton does, to the different fize of thofe 

 globules into which the vapours are condenftd ; Mr. Mel- 

 ville fuppofes, that the clouds only refleft and tranfmit 

 the fun's light ; and that, according to their different 

 altitudes, they may affume all the variety of colours at 

 fun riling and fetting, by barely reflecting the fun's inci- 

 dent light, as they receive it through a fhorter or longer 

 tra& of air : and the change produced in the fun's rays 

 by the quantity of air through which they pals, from 

 white to yellow, from yellow to orange, and laftly to 

 red, may be underilood agreeably to this hypothefis, by 

 applying to the atmofphere what fir Ifaac Newton fays 

 concerning the colour of tranfparent liquors in general, and 

 that of the infufion of lignum nephriticum in particular. 

 Edinb. Eff. vol. ii. p. 75. Bouguer Traite d'Optique, 

 p. 368. Newton's Optics, p. 228; or Prieflley's Hill, 

 of Vilion, &c. p. 436 — 449. 



BLUFF-Head, or Bluff-headed, in the Sea- Language, is 

 when a fhip has but a fmall rake forward on, being built 

 with her ftcm too Itraight up. 



Bluff-headed fnips are oppofed to thofe that are fliarp- 

 headed. They are fhorter, lefs mailed, and fail cheaper. 



BLUING OF Iron, a method of beautifying that 

 metal fometinies praftiftd ; as for mourning buckles, 

 fwords, or the hke. The manner is thus : take a piece 

 of (rrind-ftone, and whet-flone, and rub hard on the 

 work to take off the black fcurf from it ; then heat it 

 in the fire, and as it grows hot, the colour changes by 

 dfgrces, coming firft to a light, then to a dark gold co- 

 lour, and laftly to a blue. Sometimes they grind alfo 

 indigo and fallad-oil together, and rub the mixture on the 

 work with a woollen rag, while it is heating, leaving it 

 to cool of itfelf. 



B L U 



Among fculptors we alfo find mention of bluing a 

 figure of bronze, by which is meant the heating of it. 

 to prepare it for the application of gold leaf, btcaufe of 

 the bhiiih cafl it acquires in the operation. 



BLUM, Joachim Christian, iu Biography, an efleemed 

 German poet, was born at Rathenau, in 1739, and received 

 the early part of his education in his father's honfe, from a 

 lady, who was the governefs of his lifters. At the age 

 of eleven years he loll his father, and became mailer of 

 a library, of which he availed himfelf to great advantage. 

 During iiis refideuce with his mother and fillers, he amufed 

 himfelf with playing hymns on the harpCchord, and with 

 reading moral authors, and reciting orations, which he did 

 in a manner fo afi'efting as to caufe his hearers to fhed 

 tears. His mother concluded, that he had an inchnaf.on 

 to become a clergyman, and with this vitw placed him, in 

 T754, at a fchool in Brandenburg, where he nianifelied by 

 his courfe of reading, and alio by his perfoi-mances, a 

 flrong turn for poetry. In 1 7 J", he removed to the 

 gymnafiura at Berlin ; and giving up all thoughts of the 

 niinifterial office, he devoted himfelf to the fludy of phi- 

 lofphy and the belles lettres, indulging himfelf occafionally 

 in his favourite purfuit. Fro?n Berlin he proceeded, iu 

 1759, to Frankfort on the Oder, where he lludied for 

 fome time ui'.der Baum.garten, for whom he profeffed the 

 highefl refpect ; but when this city fell into the hand* 

 of the Ruffians, he j-etired to the houfe of his mother ; 

 and as his health was in an imirm and dechning flate, in 

 coiifequence of an accident which had almoff proved fatal 

 to him in his youth, he determined to continue with his 

 mother, and to devote the remainder of his days to the 

 mufcs in his native place. Here he clofed his life, Au- 

 guft 28, 1790. His poetical works were " Lyric Poems,' 

 and " Idylls," publifhed at various periods after the year 

 1763. A dramatic piece, in pi-aife of his native town, 

 entitled " Rattci:au delivered," was often reprefcnted at 

 Berhu with applaufe, but forbidden in compliance with 

 the requcfl of the Swedifh ambaffador. Blum's poetry is 

 faid to be charaAerized by foftnefs, limplicity, and correfl- 

 nefs, and he ranks among the befl poets of Germany. He 

 aKo publifhed fome volumes under the title of " Walks ;" 

 two volumes of " Orarions ;" and a colleftion of " German 

 Proverbs." His works in general were much read, and ap- 

 proved by perfons of the firfl ditlinclion. The late king of 

 Pruflia, Frederick William, honoured him with a very par- 

 ticular token of favour. As Blum's health required his re- 

 fideuce in the countr)-, he purchaied, in 1787, a fmall eflate, 

 upon which was a maiifion in a very ruinous condition ; but 

 having in the purchafeexhaufled almoft the whole of his pro- 

 perty, he could not repair his houfe without affiftance ; and, 

 therefore he addrcffed a poetical epillle to the king, in which 

 he introduced the following lines : 



" O aid thy poet, gracious prince, 

 And free his breaft from care ; 



All that he aflcs is competence 

 His manfiou to repair. 



Thofe mould'ring walls, which long have flood 

 Offenllve to the eyes, 



A temple then to gratitude. 

 Shall renovated rife. 



His grovts, near yonder wand'ring ftream, 



Whofe banks with reeds are crown'd, 

 Thus confecrattd grov.s fll;;?! fetm. 

 And fhade the hallow'd ground." 

 With this addrefs his majefly was fo much pleafed, that he 

 ordered for him 2C00 rix-doUars. Blum expreiTed his grati- 

 tude in a fecond epi'.Ue, to which the king retumed his befl 

 4 O 2 wifhes. 



