186 [Assembly 



any standard dictionary of the age, and hence the word no doubt has 

 a strange sound to well educated ears. 



To illustrate the peculiarities of the cam, models and drawings 

 would be necessar}, to make it clear to unmechanical minds; and a 

 full explanation of their qualities cannot, therefore, be given in an 

 essay upon the subject; we, however, propose, in concluding our re- 

 marks, to give at some length, the definition of the cam, in language 

 which best accords with our views of the subject. 



A cam is a revolving piece or part in machinery, the qualities of 

 which give varied motions to separate or combined parts of the same. 



Cams are of two general kinds, denominated eccentric and trans- 

 verse — indicated by the mode in which they act, whether eccentri- 

 cally to their axis, or transversely thereto; and these kinds are sub- 

 divided into opeji, grooved, and yoked cams, possessing in some 

 respects qualities common to each. 



Open cams are applied to levers vibrating eccentrically or trans- 

 versely to their planes of motion, and are usually held thereto by the 

 weight of the lever, or by a spring against the lever to insure con- 

 tinual contact with the same. 



Yoked cams are always made in a regular circular form, whose 

 axis deviates more or less from the centre, and being circular maybe 

 yoked to a vibrating bar by boxes around the circumference; they 

 are of the kind called eccentric only, and present the cam in its most 

 simple form, being but one remove from the crank, producing a regu- 

 lar reciprocating movement. 



Grooved cams have a more extensive signification and application 

 to the arts; they are both eccentric and transverse, and have simple 

 continuous grooves, in a line deviating or direct, or compound and 

 palmatcd grooves, branching into different avenues, but tending to the 

 place of beginning — the direction, in some cases, being given by 

 sliding switches at the junction of such branches. No arbitrary or 

 fixed plan can be given to a cam, to distinguish its elements of mo- 

 tion; the deviation of their course is subject to the motions required 

 in their use, and wholly dictated by circumstances; their course, like 

 the plot of a land surveyor, may be in angles, more or less zig-zag, 

 in curves or in straight lines, giving varied and different movements, 

 or suspended action to their cam levers. 



