568 Transactions of the American Institute. 



two numbers being always printed, so that hundredths of seconds 

 may be indicated. This train is primarily regulated to move uni- 

 formly by the Frauenhofer friction balls, and secondarily by an elec- 

 tro-magnet acting on the fast moving type-wheel, and controlled by 

 the standard clock. This train is entirely independent, and can be 

 stopped at pleasure, without interfering with the other type-wheels. 



II. A system of clock-work consisting of two or more shafts, car- 

 rying the type-wheels indicating the minutes and seconds. The 

 motion of this train is also governed by an electro-magnet, controlled 

 by the standard clock, operating an escapement, in a manner analo- 

 gous to the action of an ordinary clock ; every motion of the escape- 

 ment advancing the type one number. There are three type-wheels, 

 indicating minutes, seconds and hundredths of seconds. The integer 

 seconds are advanced at every oscillation of the standard pendulum ; 

 and the minute, at the end of each complete revolution of the seconds 

 wheel. The type-wheels are constructed of brass disks, around the 

 circumference of which is soldered a strip of electrotype copper, hold- 

 ing sixty numbers. 



Presuming now we have this system of type-wheels in operation, 

 it is necessary to print without disturbing their motion ; especially is 

 this true for the fast moving wheel. After a long series of experi- 

 ments, during which the fast moving wheel was detached and stopped 

 in various ways, we finally made the impression from the spring of 

 the hammer only ; not allowing the blow to fall directly on the type, 

 but arresting it about half an inch before it reached the top of the 

 type. By this device, which is regarded of the greatest importance, 

 the motion of the type is not disturbed an appreciable amount. Any 

 number of impressions following each other in rapid succession does 

 not disturb the fast moving wheel the one-hundredth part of a second. 

 By this plan, none of the type- wheels are stopped, or locked in the 

 act of printing, and records of observations may follow each other as 

 fast as the hammer can be made to deliver the blow. 



If the record is made while the type-wheel indicating integer 

 seconds is in the act of escaping, two numbers, or one number and 

 part of another, is printed, so there is never any ambiguity about the 

 record ; this condition, of course, only occurs when the fast moving 

 wheel indicates 0.95 to 0.00 seconds. If two numbers are printed 

 when, for example, the hundredths read 98, the smaller of the integer 

 seconds is the correct one. The time required for the action of the 

 escapement is about 0.06. 



The blow for printing may be struck directly, by means of a strong 



