l86 SARSEN, BASALT AND OTHER BOULDERS IN ESSEX. 
S' 
I am heartily sorry it is so late as half an hour after 6 or near 
7, and that 2 Gentlemen my Friends are this minute dropped in, 
yt I cannot have the pleasure of seeing the Flight of Ants as I now 
assuredly call them from your Specimen. I hope your health 
will permit you to observe nicely w th way they come from, & which 
way steer their course ; or do you think that the Ant hills about 
you can afford a sufficient Number for such an appearance ? Be 
pleased to observe all particulars possible, w ch I know will be 
extreamly gratefull to y e Society. The day I heard (by Dr. Sloane) 
you were in town, Mr. Pettiver & f dined w th Dr., & had all of 
us a Contest what Species the vast Flight at London last year was 
of. They were enclined to think Ichneumons : but your Specimen 
proves the contrary plainly. I am very sorry to hear that you are 
not in the best circumstances of health, w ch I heartily wish being¬ 
s' 
Your much obliged humble serv 1 
W. Derham 
Be pleased to order your serv ts to look out for them to morrow 
morning. 
The Ichneumon is a small parasitic hvmenopterous insect. 
SARSEN, BASALT AND OTHER BOULDERS 
IN ESSEX. 
BY A. E. SALTER, D.SC., F.G.S. 
[Read 1 yth December, 1910. Revised, 1914.] 
W HILE studying the Drifts of East Anglia, it has been 
my custom for several years past to note the position, 
approximate size and composition of any large or interesting 
Boulders, which I came across during my many traverses 
in that region. 
Prof. Bonney, in his Presidential Address to the British 
Association at Sheffield (1910), re-opened the question of the 
origin of the Drift. The evidence obtainable in East Anglia 
should have an important bearing upon this, especially that 
concerning large boulders, the present positions of which are 
in many cases far removed from their source of origin. 
Recently, I gathered together all the evidence I could con¬ 
cerning the boulders in Hertfordshire. This paper concerns 
those already found in Essex, and it is hoped that the subject 
will be again taken up, especially in the outlying parts of the 
