G30 PROCEEDINGS OF THE AMERICAN ACADEMY. 



the wire. But a still more serious and unexpected drawback presented 

 itself. Unless the cutting was done very slowly, the melted wax cooled 

 in the saw-carf behind the wire, leaving the edges of the cut almost as 

 firmly joined as before the wire had passed through. This, together 

 with the difficulty of holding conveniently the wax plate during the 

 process of cutting, led to the adoption of a fundamental modification. 

 Instead of holding the wax plate in such a position that the wire-saw 

 could be moved freely, it seemed that a better plan would be to move 

 the wax plate on a horizontal platform against a wire fixed in a verti- 

 cal position. Some preliminary trials were made with such a device, 

 but it soon became evident that the wire would have to be made white 

 hot if the track through the wax plate were to be made with satis- 

 factory rapidity. The disadvantages of this were obvious ; among 

 others, the wire became dangerously lax, and the desired rigidity could 

 not be maintained. The remedy which at once suggested itself, and 

 proved in the end to be practicable, was to give the wire, while keeping 

 it taut by means of a spring, a vertical play of an inch or two, as in 

 a jig-saw. By this means the w^ire surface brought in contact with the 

 wax was multiplied many times, and a sheet of wax that quickly 

 cooled down a stationary wire at the level of contact was easily melted 

 by the moving wire. 



A domestic experience in the exchange of sewing machines had 

 acquainted me with the fact that an abandoned — but not worn out — 

 sewing machine was worth about what it would fetch for old iron. I 

 selected one of fairly large proportions, and proceeded to replace the 

 needle with the electrically heated wire. It was at this juncture that 

 the mechanical skill and experience of one of my students — Mr. J. A. 

 Long — proved to be of great value. We together planned the details 

 of the alterations to be made, and he executed the most of them, no 

 professional mechanic being required at any time. The obstacle 

 which it took us longest to overcome was the freezing of the wax in 

 the track of the wire. I at first thought it would be necessary to 

 use a jet of hot air to blow the melted wax away, but found on trial 

 that a cold blast was even better, so far as getting the wax out of 

 the saw-carf was concerned, for it left a sharper cut. After removing 

 the presser-foot, in its place a blowpipe with a fine opening was 

 clamped to the presser-foot bar, and so adjusted that a blast, con- 

 ducted to it through rubber tubing, was directed downward on the wax 

 plate immediately behind the electric wire. The melted wax was 

 easily removed from the sheet, but there were two serious drawbacks 

 to the arrangement. First, the lower end of the wire where it was 

 attached to the lower end of the needle-bar became loaded with con- 



