46 Dr MacCulloch on a Detached Block qf Stone 



sures 100x101x102 = 1.030.200 turns of the measuring- 

 wheel, which, at 6^ feet, amounts to the enormous sum of 

 67.993.200 feet, or 128?| miles ; and if the time of this dis- 

 tance being performed is known within a tenth part, the mea- 

 suring may go on to ten times the above amount, or 12.877^ 

 miles, being 10.302.000 turns of the measuring-wheel ; and 

 there is no doubt that this instrument might be very valuable 

 in a manufactory, where it is of consequence to ascertain the 

 number of revolutions of any particular wheel. 



Since the " Odometer"" was presented to the Highland So- 

 ciety, I have succeeded in adapting it to the Avheel of a car- 

 riage, by having a string tied to the bottom of the instrument, 

 and joined to some fixed part of the carriage, while the end 

 of the perpetual screw is inserted into the centre of the wheel ; 

 and thus, by ascertaining the circumference of my carriage- 

 wheel, I measure the distance travelled, making a small allow- 

 ance for the carrriage not going in a perfectly straight line. 



Art. VII. — On a Singular Detached Block of Stone occupying 

 the summit qf a Hill at Dunkcld. By John MacCulloch, 

 M.D. F.R.S. F.L.S.and M.G.S. Chemist to the Board of 

 Ordnance, and Professor of Chemistry in Addiscombe Col- 

 lege. Communicated by the Author. 



Your readers, who are acquainted with the natural histo- 

 ry of Cornwall, cannot fail to recollect the theory of Dr Bor- 

 lase, respecting the detached blocks of granite so conspicuous 

 in that country, two of which, the Cheesewring near Lis- 

 keard,and the Hogging-rock, near the Lands end, I described in 

 the second volume of the Geological Transactions. Dr Bor- 

 lase's notions, however, were not exclusively his own ; as other 

 antiquaries, over whose judgments the obscurities of the Drui- 

 dical worship seem to have shed their influence, have ima- 

 gined these, and similar appearances, to be monuments of that 

 superstition or religious government, all our real knowledge 

 of which is comprised in a very few casual hints contained in 

 the Roman historians. The recent increase of attention to na- 



