Dr. Pearson's Introduction to Practical Astronomy. 453 



causes The first of this series is for the purpose of reducing ob- 

 servatTons made out of the plane of the meridian, to what they 

 would have been had they been made m that plane This method 

 of observing is particularly useful with the altitude and azimuth 

 circle There are two Tables given for this purpose : one by Ue- 

 lambre, and another somewhat more simple by the late Dr. ^oung. 

 For an account of the Tables entitled "Terrestrial Graduation, 

 we refer to the detail given by our author. 



The Tables for converting space into time, and the contrary, 

 will be found very useful on many occasions. Also the new Tables 

 for converting solar into sidereal time and the converse, with one 

 for obtaining the proportional parts of the clock's daily rate, will 

 be found equally useful. . . , 



We now come to a set of Tables of the corrections to be applied 

 to any one of the forty-eight stars for which they are calculated. 

 The object of these Tables is to obtain the mean place, the amount 

 of the several corrections, and the true apparent place of any one 

 of these forty-eight stars, for any day of the year for many years 

 to come. . . , 



This set of Tables is followed by another containing the compa- 

 rative mean places of the same forty-eight principal stars, as re- 

 cently determined by the most eminent astronomers for the epoch 



The Table in page 147 is useful as containing the changes which 

 take place in the arguments, with which the above Tables are en- 

 tered depending on the value of the subsidiary angle used in their 

 computation. By means of this Table the corrections for the forty- 

 eight principal stars may be adapted to any year for a long period 

 before or after the year 1830. ... 



The Table next in order is that of Bessel for determining by an 

 abridged method the apparent right ascensions of Dr. Maskelynes 



^ We now arrive at another class of Tables, viz. Solar Tables, of 

 which there are twenty-five, contained from page 153 to 180 inclu- 

 sive Table I. contains the mean longitudes of the sun and ot his 

 neri'cree for one hundred and fifty years, commencing with the year 

 1750 Table II. is supplementary to Table 1., and contains the 

 quantity to be added to the mean longitude of the sun, and ot his 

 mrigee, to obtain the mean longitude for any day in the above. 

 InenUoncd period. Of Tables 111. and IV., the first is for the pur- 

 nose of obtaining a nftir approximate value ot the sun s irue lon- 

 gitude as the argument with which some of the preceding lables 

 are entered ; and the last for obtaining an approximation to the 

 suns mean right ascension, for the purpose of comparing solar 

 with sidereal time. Table V. affords the means of obtaining the 

 sun^s right ascension when his longitude is given, lable V 1 con- 

 sists of the sun's declination, corresponding to every of his longi- 

 tude, with an equation for a small variation in the ob uputy. Ihc 

 vise of Table VII., containing proportional parts ot the suns daily 

 variation in longitude, is obvious. Table VIII.. entitled " Reduction 



