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Rh and the time should be taken again at the main entrance to the Star and Garter Hotel. This is a distance of 1,800 feet, having a total rise of one in fifteen, but at parts the gradient is as steep as 1 in 9$1⁄2$. The following are the times taken by cars travelling at average speeds of from four to twelve miles an hour respectively between the Dysart Arms and the Star and Garter on Petersham Hill: 5 min. 7 secs. = 4 miles per hour: 4 min. 5 secs. = 5 miles per hour: 3 min. 24 secs. = 6 miles per hour: 2 min. 55 secs. = 7 miles per hour: 2 min. 33 secs. = 8 miles per hour: 2 min. 16 secs. = 9 miles per hour: 2 min. 2 secs. = 10 miles per hour: 1 min. 51 secs. = 11 miles per hour: 1 min. 42 secs. = 12 miles per hour. As a matter of fact, the following results were obtained by experiments made during the winter when the roads were heavy between the Dysart Arms and Star and Garter entrance, with flying start:

A contour of Petersham Hill is illustrated opposite.

Purchasers who live in hilly countries often ascertain from local surveyors what are the stiffest gradients on surrounding hills. They then go to London to purchase a car and ask the makers if it will ascend 1 in 8$1⁄2$. An agent has been known to say 'yes,' and, in proof of this statement, the purchaser has been driven up to Savoy Street and has been told it is 1 in 8$1⁄2$. In order to assist purchasers, the engineer of the City of Westminster has kindly supplied a correct contour of Savoy Street which is published (p. 60), and from this it will be seen that the average gradient is 1 in 13·4 and the steepest is 1 in 11·24. Another hill, a really steep one, has also been specially surveyed for the purpose of this book, and the contour is published (p. 61).