326 Mr. J» N. Hearder on a new Instrument for Registering 



by the delay in the publication of his work. Dr. Noad having 

 considered these remarks to imply an accusation of plagiarism, 

 I take this opportunity of stating that I did not intend them to 

 convey any such imputation, and that I only wished to complain 

 that Dr. Noad had done me an injustice and a serious commer- 

 cial injury by suppressing my invention, and giving publicity 

 and precedence to another production of more recent date, and 

 almost identical with my own. 



During the past nine months I have had opportunities of still 

 further extending the principle upon which my machine is con- 

 structed, and with a corresponding increase of power ; since I 

 have occasionally, from a single machine, produced sparks 

 4 inches in length in free air, and I have very little doubt that 

 I could construct machines to give sparks of 12 inches or more. 



The results obtained by this increase of power are veiy striking, 

 and phsenomena previously unknown are continually developing 

 themselves. I have before alluded to two different classes of 

 thermal effects obtained : first, from the simple spark between 

 the terminals ; and secondly, from the spark pi'oduced through 

 the intervention of the Leyden jar. The simple spark passing 

 between the terminals is comparatively soft and attenuated, 

 though when of considerable length it is accompanied by a 

 tolerably sharp snap. Sparks of 2 to 3 inches in length are 

 extremely crooked, the deflections sometimes increasing the 

 length of the spark to nearly one-half more than the distance 

 between the terminals. Imperfect conductors, such as paper or 

 wood, assist the spax'k in overleaping the interval; for if the 

 points be placed beyond the striking distance, and a sheet of 

 paper be held parallel to them and nearly an inch distant from 

 each, sparks will frequently pass from one point to the paper 

 and across its surface to the other point. In this way I have 

 often obtained sparks nearly 6 inches in length. 



The chief characteristic of this spark is its power of igniting 

 or burning substances which are either non-conductors or bad 

 conductors ; and some of these effects are very remai'kable. 



On one occasion, when experimenting with one of my large 

 coils, two wires from the terminals were accidentally lying with 

 their ends at a distance of several inches from each other upon 

 the table. I happened to set the machine in action, and instantly 

 the table burst into flame in the two spots on which the ends of 

 the wires rested, and the combustion went on rapidly increasing 

 until I stopped the machine. Noticing this, I took a piece of 

 deal and slightly moistened its surface with nitric acid and placed 

 it on the table of the universal discharger, with the points about 

 4 inches apart. On connecting it with the machine, the com- 

 bustion commenced at the points as before, and the flames ad- 



