I used to think that Whitefield was a good place to find erratics because of the dense bedrock, common in our Sheepscot River Valley that helped guide the glaciers into a narrow relative deep channel - all the while widening and deepening the "Sheepscot valley".
That sharp bedrock channel scraped the glaciers sides as it slowly progress, then retreated .

BUT, when I checked with Robert G. Marvinney, our State Geologist, he said " Actually, the continental glacier overtopped the entire state and was at least a mile thick, maybe two, in the Whitefield area.  All the ice flow indicators that we have found in the region show transport from the northwest to the southeast, not parallel to the bedrock (northeast-southwest) nor the river.  However, the hard rock, with many fractures, allowed large blocks to be plucked by the glacier and deposited somewhere “down glacier” when the glacier melted."
 And when I said that I believed that scraping dislodged some of these larger (erratic) rocks, not unlike mosquitoes off a moose in the brush.
( the smaller sized stones and gravel were plowed up into "eskers" - ridges of gravel usually atop a clay base -much like we find on the West side of Vigue road.) I have seen two clam "flats" in that blue clay on Longfellow hill and beside Chamberlain brook. The smell of those 10,000 year old clams was the same as today 's flats in Wiscasset.

He replied " Eskers form by flowing melt water in tunnels beneath the glacial ice, not by “plowing” of sedimentary materials by the prow of the glacier.  Ridges formed by plowing or deposition of material at the leading edge of a melting glacier are called moraines.  They are made of till – a mixture of every size material from clay to boulders – which is quite different from the sorted sand and gravel (little silt or clay) common in eskers"

We are so fortunate to have these experts at our beck and call... !

 

What are glacial erratics?
 

What about " ice rafted erratics "??


more info

and here...THE WORLDS LARGEST ERRATIC !!