24 On the Theory of the Dead Escapement. 



during- its ascent and descent, in the arc of vibration, I do not ap- 

 prehend the distinction to be very material. Now as all irregula- 

 rities resulting from the train of wheels, must be more felt during 

 the period the impulse is being given, than during the period of 

 rest, it follows that on that account a low (or short) angle of lead 

 is much preferable to a high one. 



It is also worthy of notice, that in the case supposed above, of 

 two pendulums made to vibrate equal angles, by the action of 

 dead escapements similar, except in the quantity of the angle of 

 lead; the pendulum applied to the pallets with the high angle, 

 will be much more liable to come to rest than the other, on ac- 

 count of the excess of the angle of vibration, over and above the 

 angle of lead being less than in the case of the pallets with a low 

 angle of lead. 



In a former paper, (see Vol. xiv. p. 334.) I described a new 

 mode of constructing the pallets and their parts, by which great 

 accuracy in the execution of the escapement is obtained. It might 

 appear requisite that I should, to complete the description of the 

 dead escapement, describe the method of dividing and cutting the 

 teeth of the 'scape wheel. But the subject of dividing and cutting 

 wheels has been so fully entered into, and so much has been 

 written on the subject, and much to the purpose, by various au- 

 thors, who have written on clocks and watches, that it is quite su- 

 perfluous to add any thing further on the subject. 



Art. II. Account of the Remains of a Roman Camp at 

 Mitchley, near Birmingham. By John Finch, Esq. 



[Id a Letter to the Editor.] 



Sill, Birmingham, Sept. 24, 1822. 



Mitchley Camp is situated three miles south-west of Birming- 

 ham, near the village of Harborne, and is the property of the Right 

 Hon. Lord Calthorpe. It is noticed by Mr. Hutton, in his valua- 

 ble history of this town. The exterior vallum is 330 yards long, 

 and 228 wide (by a measurement made as accurately as the ground 



