682 PHILOSOPHICAL TRANSACTIONS. [aNNO 17 4g. 



posed to a violent fire. As I am the first, says Mr. B. that has mentioned this 

 notable circumstance, be pleased to let me have the honour of this improvement 

 in the Phil. Trans. 



Of an Extraordinary Rainbow, observed July 18, 1748. By Peter Daval, 



Esq. Sec.R.S. N° 493, p. 193. 



On Monday July 18, 1748, about a quarter before 7 in the evening, the 

 weather being temperate, and the wind about n.n.w., walking in the fields be- 

 yond Islington, Mr. D. saw a distant rainbow, which appeared to take in a large 

 portion of the heavens ; but had nothing remarkable, and vanished by degrees. 

 Continuing his walk, about 20 minutes after the disappearing of the first rain- 

 bow, a rainy cloud crossed him, moving gently with the wind, which exhibited 

 a more perfect and distinct rainbow, than he had ever before seen ; in which he 

 could plainly distinguish all the secondary orders of colours noticed by the late 

 Dr. Langwith, in his letters published in the Philos. Trans. N° 375, that is, 

 within the purple of the common rainbow, there were arches of the following 

 colours: 1. Yellowish green, darker green, purple. 2. Green, purple. 3. 

 Green, purple. 



Of the Present Condition of the Roman Camp at Castor in Norfolk, with a Plan 

 of it; also a Representation of a Halo or Mock- Sun observed July 11, 1749. 

 By Mr. Wm. Arderon, F.R.S. N° 493, p. 196. 



The town of Castor is at present in a very low condition, containing no more 

 than between 20 and 30 small cottages. It stands about 4 miles south-west of 

 Norwich, and by tradition, and some learned authors, is supposed to have been 

 a considerable city, out of whose ruins Norwich took its rise. However, at this 

 day, excepting the camp, not the least trace or footstep of any thing remarkable 

 is left remaining. 



The camp itself lies near a furlong south-west from the town of Castor, and 

 leads you by a gentle descent down to the little river Wentsum, which swiftly 

 glides close to the end of it, and doubtless at the first forming of the camp was 

 designed to be part of the fortification on that side, as well as to supply the army 

 with water, and to bring up such things as they wanted from the sea, if their 

 communication by land should at any time be impeded. This river is by some 

 called Taus, or Tese : but probably it did not formerly take that name till it ap- 

 proached the Roman camp at Teseburgh, 3 or 4 miles higher. 



We are told by tradition, as well as by some learned authors, that the sea 

 came up to this camp ; and indeed every intelligent observer must confess, that 

 the marine bodies found in every part of Norfolk, on the highest hills, as well 

 as in the lowest pits and valleys, are indubitable proofs, that at some time or 



