J86 Reply to Mf. Allan's Observations [April, 



1. On the Rectification of the Hyperbola by means of two 

 Ellipses ; proving that method to be circuitous, and such as re- 

 quires much more calculation than is requisite by an appropriate 

 theorem ; in which process a new theorem for the rectification of 

 that curve is discovered. To which are added some farther obser- 

 vations on the rectification of the hyperbola : among which the 

 great advantage of descending series over ascending series in many 

 cases i- clearly shown ; and several methods are given for com- 

 puting the conitant quantity by which those series diifer from each 

 other. By the Rev. John Hellins, B.D. F.R.S., and Vicar of 

 Potter's Fury in Northamptonshire. 



2. On the Solar Eclipse which is said to have been predicted by 

 Thales. By Francis Baily, Esq. 



S. Account of a Lithological Survey of Schehallien, made in 

 order to determine the specific gravity of the rocks which compose 

 that mountain. By John Playfair, Esq. F.R.S. 



4w On the Grounds of the Method which Laplace has given in 

 the second Chapter of the third Book of his JNIecanique Celeste 

 for computing the Attractions of Spheroids of every Description, 

 By James Ivory, A. M. 



5. On the Attractions of an extensive Class of Spheroids. By 

 J. Ivory, A. M. 



6. On the Attraction of such Solids as are terminated by Planes ; 

 and of Solids of greatest Attraction. By Thomas Knight, Esq. 



7. Of the Penetration of a Hemisphere by an indefinite Num- 

 ber of equal and similar Cylinders. By Thomas Knight, Esq. 



8. Observations on the Measurement of three Degrees of the 

 Meridian, conducted in England by Lieut. Col. Mudge. By Don 

 Joseph Rodriguez. 



How came Dr. Gregory in the preceding letter to omit men- 

 tioning the four other mathematical papers contained in the same 

 volume of the Transactions in which Don Rodriguez' paper it 

 printed?* 



Article X. 



Reply to Mr. Allan^s addilional Observations on Transition Rocks. 

 By James Grierson, M. D. 



(To Dr. Thomson.) 



SIR, 



I PKRCEiVE, in the Annals of Philosophy for this month, aa 



answer from Mr. Allan to my observations on transition rocks, 



which were published in your Number for August last ; and in 



offering a few words in reply, which I think it necessary to do, I 



♦ As it never was intended, by the Editor, U\a.t the ^nnah of Philosophy sho\i\A 

 he made a vehicle for controversy, it is thouglit necessary to state here that no 

 farther communication on this subject can be admitted. 



