APPENDIX. 



SIMPLE APPARATUS FOR ILLUSTRATING MECHANICAL 

 PRINCIPLES. 



For the assistance of lecturers, teachers, and home students, the fol- 

 lowing list is given of cheap and simple apparatus and materials for 

 performing most of the experiments described in the first part of this 

 work. These experiments, although simple, exhibit principles of much 

 practical importance. 



1. Inertia apparatus, p. 13. The concave post or stand is sufficient, 

 the snapping being done by the finger, although a spring-snap performs 

 the experiment more perfectl}'. 



2. Weight with two hooks and fine thread, p. 13. 



3. The inertia of falling bodies may be simply shown, and the pile- 

 engine illustrated, by placing a large wooden peg or rod upright in a 

 box of sand, and then dropping a weight upon its head at different 

 heights, which will drive the rod into the sand more or less, according 

 to the distance passed through by tlie falling weight. 



4. A straw-cutter, so made that the fl3"-wheel can be easily taken off, 

 will show in a very striking manner the efficacy of this regulator of 

 force. 



5. Two lead musket balls Avill exhibit the experiment in cohesion, 

 p. 27. Balls or lead Aveights with hooks may be separated by sus- 

 pending weights, to show the amount of force required to draw tliem 

 asunder. Metallic buttons or plates an inch in diameter, with hooks, 

 will show the great strength needed to separate them when coated with 

 grease, p. 27. 



6. Capillary tubes of different sizes, two straight small panes of glass, 

 and a vessel of water, highly colored with cochineal or other dye, to ex- 

 Libit capillary attraction. 



7. Glass tube, piece of bladder, and alcohol, for experiment described 

 on p. 33. 



8. The cylinder for rolling up the inclined plane, represented by 

 fig. 18, p. 34, may be very easily made by using a round pasteboard 

 box a few inches in diameter, and securing a jnece of lead inside by 

 loops made with a needle and thread. The object shown by fig. 19 

 may be cut in one piece out of a pine shingle, the centre rod being 

 lengthwise with the grain ; the two extremities are shaved small, and 

 Avound with thick sheet-lead, and the whole then colored or painted a 



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