APPENDIX VI. THE AGE-RECKONER 



IN making records of growth it is advantageous to weigh 

 the animals at definite ages, using the same ages in all cases. 

 As it is somewhat laborious to calculate the proper dates 

 for an animal born on a given day, the age-reckoner, herewith 

 figured, was devised. It does away with all calculation, for after 

 setting the machine for a given birth-date, all the dates on which 

 weighings are to be made can be read off at once. The 

 apparatus as shown in the figure consists of two metal 

 wheels close together on a single axle. The rims of the wheels 

 are broad and each one bears 365 lines, one for each day 

 in the year. The right-hand wheel is inscribed with the months 

 and days of the month, for example, "Nov." marks November 

 ist, the numbers below November 5th, I5th, and 25th. "Dec" 

 marks December ist. This wheel which bears the dates may be 

 called the " calendar wheel" and is attached permanently upon 

 the axis. The left or " age wheel" can be revolved without turn- 

 ing the axis, so that it can be set with its zero line opposite any 

 date on the calendar wheel; it can then, by means of the set screw 

 seen in the figure, be clamped to the axle, and both wheels will 

 then revolve together. Upon the age wheel the ages are marked, 

 for every ten days up to 210, thereafter every thirty for five 

 months. Obviously after the age wheel has been set with its zero 

 at the date of birth and been clamped, all the ages selected for 

 weighing will fall opposite the proper dates, and may be read off 

 by simply revolving the two wheels. 



It was the usual practice as soon as an animal (or litter) was 

 born to set the age-reckoner, and then copy down from it on 



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