Description of a Printing Chronograph. By Prof. G. 

 W. Hough, Director of the Dudley Observatory. 



[Read before the Albany Institute, May 2, 1871 .] 



About the year 1848, the idea of recording astronomical 

 observations, by the use of galvanic electricity, was put in 

 successful operation by different individuals. Since that 

 time chronographs of various forms have been constructed 

 for recording in a legible manner on a moving sheet of 

 paper the time of any phenomenon observed. The great 

 superiority, in point of accuracy and saving of labor over 

 the old eye and ear method, formerly used, led to the 

 almost general adoption of the new plan. 



During the past ten years the idea of constructing a 

 chronograph, which should print with type the time of the 

 observation, has been entertained by a number of persons. 

 About five years since Prof. Hilgard, of the Coast Survey, 

 read a description of an apparatus designed for this pur- 

 pose, and about the same time Prof. C. A. Young, of Dart- 

 mouth College, published a proposed plan for one, in 

 Silliman's Journal of Science. But, so far as we are in- 

 formed, the mechanical construction of such an apparatus 

 has not heretofore been attempted by any one. 



The construction of a machine which shall carry a type 

 wheel capable of giving impressions, with uniform velocity 

 for a number of hours together, without sensible variation 

 in its motion, is a problem which is not easy of solution. 



Some five or six years ago, in a paper read before the 

 Albany Institute, I gave an account of the method I pro- 

 posed to adopt, and in the construction of the machine, 

 now to be described, the plan then proposed has been gene- 

 rally followed. My plan, which is radically different from 



