March 25, 1909J 



NATURE 



97 



THE BOTALLEK CIRCLES. 



BORLASE, in his " Antiquities of Cornwall " 

 (p. 199), published in 1769, refers to what he 

 terms " tlie curious cluster " of circles at Botallek, 



e% .-.••. 



v-----.^ 





the seeming confusion of which led him to write 

 " \ cannot but think that there was some mystical 

 meaning, or, at least, distinct allotments ^., 



to particular uses." ,'^- — -^^ 



Fortunately for science, he accompanies r-' 

 his account with a plan, ev-idently care- 

 fully prepared (Fig. 1), which is now the 

 only thing that remains; every stone has 

 been utilised in building an engine house, 

 or in other ways. Only the site is shown 

 ordnance map. 



As the " cluster " of circles exceeds in elaboration 

 anything of the kind with which I am acquainted, it 

 was of great interest to see if anything could be made 

 of it in the light of other researches in Cornwall, and 

 I propose now to state the result in a very abridged 

 form. Fuller details I have communicated to the 

 Royal Society.' The first point of inquirv concerned 

 the N. point given on the plan — whether it was true or 

 magnetic. A perusal of Borlase's volume showed 

 that he was fully acquainted with the necessity of 

 referring in such descriptions to the true north, instead 

 of, as he says, " such an inconstant and fluctuating 

 index as the declination of the needle, which is not 



1 Proc. Roy. Soc, March, 1909. 

 NO, 2056, VOL. So] 



only different in different places, but varies also at 

 different times in one and the same place " (p. 115). 



When this point was settled, it became evident at 

 once, when the circles were completed and lines drawn 

 from centre to centre, that approximately the same 

 azimuths were in question as those met with in other 

 Cornish circles. 



Borlase docs not give the heights of hills. I there- 

 fore asked Mr. Thomas, an active member of the 

 Cornish Society for the Astronomical Study of Ancient 

 Monuments, to observe them for me. 



.■\mong the azimuths were two, the first from the 

 approximate centre of the circle F to the approximate 

 centre of E, N. %f E., and the second, from the 

 appro.'wimate centre -of F to that of H, S. 66° E. In 

 sending his results to me Mr. Thomas remarked that 

 the former line passes over the Carn Bean barrow 

 and the latter passes 2^° to the N. of the Goon Rith 

 barrow; thus the azimuth of the Goon Rith barrow 

 would be S. 63^° E. This enabled- me to check the 

 accuracy of Borlase's N. point. 



The two alignments to two still existing barrows 



are common to Botallek and other monuments in 



Cornwall. On the assumption of identity of object, 



Borlase's orientation was true, and not magnetic, 



and, also, was not far from the mark. 



The next step was to make a very careful deter- 

 ' mination of the centres of the circles, and it 

 ^ was found that the line, centre of F to centre of 

 H, coincided with the line S. 63° 45' E. from the 

 J former to the Goon Rith barrow. In other words, 

 the difference between the azimuth we had provi- 

 sionally determined from the circles and that of 

 Goon Rith barrow was due to an error of centring, 

 • and no doubt was left that the line between the 

 : centres of F anci H was really directed to the 

 f barrow. Similarly the line N. 83° E. joining the 

 centres of F and E was directed tovthe Carn Bean 

 barrow. Both these lines were' recognised as 

 familiar, giving, approximately, the November 

 sunrise and the heliacal rising of the Pleiades in 

 May respectively. In the case of the S.E. azimuth 

 there is an alternative explanation of the sight- 

 line. Both in Cornwall and Wales we have 

 found that azimuth-marks (barrows, &c.) were 

 sometimes erected so that they gave the direction 

 of sunrise a fortnight or three weeks before the 

 critical date. I therefore decided to adopt the 



Pleiades azimuth, N. 83° E., as the fundamental 

 line by which to fix the N. point, and it followed 



