CABLES strength o/ See Cords. 



CALENDAR. 



The civil year consists of 365 days ; the real tropical year of 365d. 5&. 

 48m. 51,6*. The excess therefore of the tropical year amounts to nearly 

 24 hours, or one day, in four years. Hence the necessity of intercalating 

 a day every fourth year, effected by making February contain 29 days. 

 This correction was first applied by Julius Caesar, and the year on which 

 it fell was called by him Bissextile, by us Leap year. As it occurs every 

 4th year, and every 100th year was a leap year in the Julian account, it 

 follows that every year divisible by four is a leap year. This correction 

 is evidently too great by nearly twelve minutes, which would amount to 

 one day in about 129 years. By the omission of this second correction, 

 an error crept into the calendar, which was first amended by Pope Gre- 

 gory, in 1582, who wishing to bring the vernal equinox to the 21st of 

 March, the day on which it happened in the year 325, when the council 

 of Nice was held, suppressed 10 days. The correction of the stile did not 

 take place in England till 1752, at which time a suppression of 11 days 

 became necessary. This is called by us the new stile. To correct the 

 error in future, three intercalary days are omitted every 400 years. 

 Thus the centenary years 1700, 1800, 1900, which ought to have been 

 leap years, were ordered not to be so ; and the same in 2100, 2200, 2300, 

 and so on for succeeding centuries. The error of the calendar, as at pre- 

 sent constituted, will not amount to one day in less than 4237 years. 



CAPILLARY Tubes. (Ptoyfair.) 



1. The height to which water rises, and mercury sinks, in capillary 

 tubes, varies inversely as the diameter of the tubes. 



If the bore is -r^ th of an inch, the rise is 5,3 inches. 



2. If a capillary tube, composed of two cylinders of different bores, be 

 immersed in water, first with the widest part down ward, and afterwards 

 with the narrowest, the water will rise in both cases to the same height. 



3. If two plates of glass be kept parallel and near to one another, and 

 if their ends be immersed in water, the water will ascend between them 

 to half the height it would rise to in a tube having its diameter equal to 

 the distance of the plates. 



When the plates make an angle with one another, if they be immerse^ 



