usually , when he was out on an errand his entire being was fixated upon all the fascinating sights that the streets of london had to offerthe tantalizing goods on display at the shops , the deft movements of the carriage drivers as they maneuvered their prancing horses around a sharp curve , the shouts of the street hawkers as they cried out their songs of fresh milk and new potatoes , sharp knives and old clothes , and a dozen other interesting things .