30 
All are good positions for easy observation, neither too near the 
horizon nor so high as to oblige the head to be raised. The 
transits of three of our stars would be at some distance above the 
edges of their piquet stones. But any difficulty arising from this 
would be easily surmounted. For the observer needed only to 
hold in his hand a staff, say 6 feet long, having a straight edge. 
This he would rest on the ground in front of himself, and keeping 
the straight edge of the staff in line with the vertical edge of the 
‘stone he would know the instant of transit over the stone ; for it 
would be exactly when the star touched the edge of the staff. 
It may also be of interest that the angles should be known 
which the heights of the several piquet stones at their respective 
distances from the stations afford. There are 25° 41’ 13”; 
35° '5' 36" 5 25° 54 13" 5 23° 12 17”. 
My theory is now before you. I wish I could have explained 
it in fewer words. I should be glad if the result of our investi- 
gation might be as satisfactory to you as it was gratifying to me. 
No reason that seems to me worth much consideration had 
heretofore been suggested for the existence of those two outlying 
stones and mounds ; and I supposed that my idea had been tried 
and found impracticable. Therefore surprise as well as pleasure 
were mine as, when the figures were being worked out, star after 
star appeared answering within a second of time to the angles 
proclaimed by those massive rocks ; and it is to me a marvel how 
the builders could have planted those huge stones in such nicety 
of agreement with these angles. 
POSSIBLE SOURCES OF ERROR IN THE CALCULATIONS. 
Moreover, there existed possible sources of error which might 
have detracted from the desired exactness of the results from the 
calculations involved. Thus: I have not burdened the sums 
for finding the Sun’s amplitude from East with deductions for 
for parallax or increase in the temperature ; nor have I made any 
addition in altitude of the stars for refraction ; also there is the 
: 
4 
| 
) 
| 
/ 
