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52 Friday June 9th 1843
  The idea occurred to me while in Phi[[superscript]]o[[/superscript]]. that possibly the emination from the electrical spark was not of the same intensity throughout the whole line of the discharge, and perhaps it might be compared to the poles of the discharging wires. To test this, a [[strikethrough]] hole [[/strikethrough]] [[insertion]] slit [[/insertion]] was made in two plates and these slits were placed transversely to the path of the spark so that the lines underneath could not be reached by the emination except from a single point of the spark, with this arrangement it was found that the light was produced from every part of the line of the discharge, but that it was much more intense at the two ends. 
   To test this more accurately another arrangement was made by which the impression from the line could be made at once from several points, and the intensity of the action [[insertion]] from each [[/insertion]] compaired at once with one another. For this purpose three holes were cut in a plate of mica [[strikethrough]]and the [[/strikethrough]] so that one hole would be directly under each pole of the discharger and the other be midway between the other two. When the discharge was made close to the plate of mica, so that the emination [[strikethrough]] from [[/strikethrough]] [[insertion]] through [[/insertion]] each hole might make its impression on one spot without any effect from other parts of the spark; the impression at the middle hole produced a faint phosphorescence which continued a few seconds and then disappeared while those at the two ends continued to glow for more than a minute. I have called the openings holes, they were rather slits, so that the impressions from the whole width of the spark might be viewable [[strikethrough]]from [[/strikethrough]] on the line through each slit.  [[Image at bottom of page of a rectangle with the three slits]]
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Oct. 3-1843                  
Heat of a thunder cloud -  53

Since the last date, I have been engaged in college and other duties, an I am now for the first time since then enabled to resum the business of experimenting. This being our autumnal vacation, I hope to have a few weeks of uninterrupted leasure. I must however make the best use of this since on account of the new arrangements of college vacations during the next year, my time will be more than usually occupied. 
  [[illustration in the left margin of a tubular device on a pole that resembles a windsock fully extended, might be a telescope.]]
  Agreeably to the suggestion given at page 30, during the summer I have [[insertion]] had [[/insertion]] attached to the thermo pile of Melloni's apparatus a tube of pasteboard covered on the outside with gilt paper inorder to reflect the heat from the outside. The object of the tube is to screen the pile from all radiation except such as proceeds from some circumscribed portion of space. The instrument thus furnished gave very satisfactory and interesting results. When turned towards a cloud of a white appearance, it indicated an increase of temperature over that of the blue sky, the needle taraversing in some cases an arc equal to 50 degrees.
   As the instrument was lowered towards the horizon, the heat was increased-the experiment being repeated in the forenoon and afternoon, but perhaps the result would be different were the observation made early in the morning or late in the eveng, or rather after sundown.
   When the instrument was [[jesccled?]] to a dark thunder cloud, it indicated [[strikethrough]] an [[/strikethrough]] a diminution of temperature. This is in accordance with the theory of Peltier.
   Found the heat decreased towards eveng, from the smith downwards.