684 PHILOSOPHICAL TIIANSACTIONS. [aNNO 1749. 



mixed ; when burnt, one appears red and the other white : at the time of view- 

 ing them, they were exceedingly hard and solid, and far superior to any thing of 

 the kind now made with us. Perhaps they are little worse than when they were 

 first laid down. These bricks were made without the assistance or addition of 

 sand, as is too much the practice at present here in Norfolk : for when sand en- 

 ters the composition in any considerable proportion, it renders the bricks friable, 

 soft, and rotten, subject to be broken or ground to pieces with the least motion 

 or pressure. The length of these bricks is 17-rir inches, or a Roman foot and 

 half; and their breadth ll-jV inches, or precisely a Roman foot: which may 

 serve as some proof that the Roman measures, handed down to us by several 

 authors, are right, and may likewise inform us of the proportionable stature of 

 man at that time. The thickness of these bricks is 1-^ inch. 



The great number of Roman medals that have been, and still are found in and 

 about this camp, are a matter of great wonder. One lady who lives near the 

 place^ has it seems picked up at least 100 ; and several are daily gathered up by 

 boySj and sold to strangers who come to visit the place. That these pieces have 

 been used as money seems exceedingly clear, from their different degrees of per- 

 fection ; some being worn almost quite smooth, others having imperfect busts 

 without letters, and others again having both the busts and inscriptions fair and 

 legible, which could only happen from their different wear as money. 



A particular kind of halo was observed at Norwich, on the 11th of July 1749, 

 At 5 o'clock in the evening : the colours were exceedingly vivid^ and the centre 

 of it, contrary to what he ever yet saw, was not in the sun, but in the zenith. 

 The sun's rays shone through the clouds at the same time, as they frequently do 

 when the sun is near the horizon. 



Part of a Letter from Leonard. Euler, Prof. Math, at Berlin, andF.R.S. To 

 the Rev. Mr. Caspar JVetstein, concerning the Gradual approach of the Earth 

 to the Sun. Dated Berlin, June 28, 17 AQ. Translated from the French, by 

 S. T., M.D., F.R.S. W 493, p. 203. 



M. le Monnier writes to me, that there is at Leyden an Arabic manuscript of 

 Ibn jounis (if I am not mistaken in the name, for it is not distinctly written in 

 the letter), which contains a history of astronomical observations. M. le Mon- 

 nier says, that he insisted strongly on publishing a good translation of that book. 

 And as such a work would contribute much to the improvement of astronomy, I 

 should be glad to see it published. I am very impatient to see such a work which 

 contains observations, that are not so old as those recorded by Ptolemy. For 

 having carefully examined the modern observations of the sun with those of some 

 centuries past, though I have not gone farther back than the 15 th century, in 

 which I have found Walther's observations made at Nuremberg ; yet I have ob- 



