124 ANNUAL OF SCIENTIFIC DISCOVERY. 



FIXING LEAD-PENCIL, CHARCOAL, AND CHALK DRAWINGS. 



TV. Wolanek states, that when the paper containing drawings 

 or writings made with lead pencil, charcoal, etc., is painted 

 over on the reverse side (where no writing or drawing exists) 

 with a moderately strong solution of bleached shellac in alcohol 

 the same becomes thoroughly fixed, so that they cannot b<j 

 rubbed off. Journal Franklin Institute. 



NOVEL MECHANICAL MOVEMENT. 



All exceedingly ingenious substitute, which can be scarcely 

 called a modification, of the well-known joint of Dr. Hooke, has 

 been patented within a year, by Mr. Melville Clemens, of Boston, 

 an illustration and long description of which has been published 

 in "Engineering," London, September 2, 1870. 



Except, to a very careful reader and student, this description is 

 somewhat appalling (beside involving some errors of statement 

 and calculation), and the drawings fail to show clearly or readily 

 the principle on which it is constructed. In fact, the parts lie at 

 such angles with each other, that neither drawings nor perspective 

 will convey an adequate idea of the contrivance. It gives the full 

 range of 90 to the angle at which the shafts (in the same plane 

 of rotation) may have, and the motion transmitted is a uniform 

 angular one, ' both of which conditions are advantages not pos- 

 sessed by the Hooke joint. 



If it is imagined that 2 shafts are placed in boxes or pedes- 

 tals in the same plane, but at any angle with each other from 

 to 90, the ends of which are tee-headed and placed at such dis- 

 tance apart that the tee-heads will clear each other (at 90) in 

 rotating; and if it is further supposed that each tee-head is made 

 the axis or knuckle of 2 straps or triangular hinges, and the 

 outer extremities of the hinges are connected (in pairs) with 

 those which are attached to the opposite tee-head in a ball-joint, 

 the whole forming a hinged parallelogram, the gist of the con- 

 struction will be comprehended. 



The ball-joint must allow a pestle and mortar motion of 10 to 

 15 and a rocking motion of 45, and the knuckles on the tee- 

 heads must rock 90 while the system rotates. 



In a practical form for use the joints of this arrangement admit 

 of as great strength as the Hooke joint, and the extreme range of 

 angle to which it is applicable will render it available in many 

 places. 



The study of mechanical movements has occupied so many and 

 so able persons, that the addition of a novel one bespeaks more 

 than usual ingenuity; and this Clemens joint will at once take a 

 place in the repertory of general information. Journal Franklin 

 Institute. 



