168 GERARD I REGNERI FOCKENS 



^l passed slJII more soulherly lliati in Ihe former obscrvntions^ Tbis srxisible alteration 

 if the more siirprized us, in ihat it was the coatrary way from \\h:it it would have 

 « been, had it proceeded from an annual parallai of Üie slar, But being now pretly 

 <( well salisfied, Üjal it could not be enlirely owing lo the waut of exactness in the ob- 

 « serrations ; and having no nolion of any thing eise, tlial could cause such an appea- 

 « rent molion as this in the slar ; we began to tliink tha-t some cbange in Ihe mate- 

 « rials, etc. of the instrument itself, might have occasioned it^ Under these apprehen- 

 (i sions we remained some time , but being at lenglh fully convinced , by several trials, 

 « of the gwal exactness of the Instrument, and finding by the gradual increase of the 

 « Stars distance from the pole, that there must be some regulär cause that produced it; 

 « we took care to examine nicely , at the time of each Observation, how rauch it was: 

 « and about the bcginning of March 1726, the slar was foumd to be 20" more sou- 

 « therly thau at the time of Ihe lirst observatioa. It now indeed seemed to have arrived 

 (( at its titmost limit southward, because in several trials made about this time, no len- 

 « sible differeMe was observed in its Situation. By the middle of April it appeared to 

 « be returning back again lowards the north; and about the beginning of Jime it passed 

 « at ihe same distance from liie zenith as it had done in December , when it was ßrst 

 « observed. 



« From the quicic alteralion of this slar's declination about this time ( it increasing a 

 « second in three days) it was concluded, that it would now proceed northward , as 

 « it before liad gone southward of its present Situation ; and it happened as was cpn- 

 « jeclured: for the star continued to move nortlrs-ard tili September following, when 

 « it again became stalionary , being then near 20' more northerly than in June, and^ no 

 « less than 39" more northerly than it was in March. From September the star relur- 

 t nod towards the south, tili it arrived in December to the same Situation it was in 

 « at that time twelve months, allowing for the difference of declination oji aqcoiint of 

 « the precession of the equinox. 



« This was a sufficient proof , that the insrument had not been the cause of this af»- 

 <f parent motion of the slar, and to find one adequate to such an efFect seemed a diffi- 

 « ciilty. A nutation of the earlhs axis was one of the first things that offered itself upon 

 « this occasion , but it was soon found lo be insufiicient : for Ihough it miglit have ac- 

 « counted for the change of d«clination in y Draconis , ^yet it would not at the same 

 « time , agree wilh the phaenomefia in other Stars ; particularly in a small one almost 

 « opposile in right ascension to y Draconis, at about the same distance from the aorlli 

 « pole of the equator. For Ihough this star seemed to move the same way , as a nula- 

 « lion of the earth's axis would have made it , yet it chauging its declination but about 

 « half as jBuch as y JDraconis in the same sime ( as appeared, upoü com^aring the phser- 



( ,. ' " « va- 



