Intelligence and Miscellaneous Articles. 563 



of Science (vol. xlvi. p. 235), I gave my reasons for classing these 

 two minerals with heulandite. That beaumontite is heulandite, I 

 believe is no longer doubted in this country or Europe. An analysis 

 of the mineral by M. Delesse, has appeared since the publication of 

 my paper*, and it agrees with all the other analyses of heulandite, 

 excepting in the slight excess of silicic acid. In this respect it offers 

 an example analogous to that of the variety of chabasite called aca- 

 diolite, in which the silicic acid forms a larger atomic proportion of 

 the mineral, without causing any appreciable variation in the angles 

 of the crystals. As to lincolnite, I must think that the various 

 papers that have been called forth in relation to it since my first 

 communication appeared, have established its indisputable identity 

 with heulandite. 



Peculiarities in the modifying planes \ have given rise to a secon- 

 dary form, rarely observed in heulandite. These consist in the en- 

 largement of the planes/ (Phillips), or e (Dajia), so as nearly to ob- 

 literate the primary planes M; being, in fact, the reverse of what we 

 usually observe in heulandite from other localities. In the measure- 

 ments by Prof. Hitchcock and Prof. Shepard, the angle of / on T 

 was mistaken for that of M on T, and in the figure given by Prof. 

 Hitchcock, it is evident that the planes lettered M should be/. The 

 true value of / on T is 115° 10' (Dana) ; Prof. Shepard's last mea- 

 surements made it 116° 17'. 



Ledererite. 

 I am compelled, at last, to declare my conviction that the specific 

 nature of this mineral can no longer be maintained. Council's ana- 

 lysis of an Irish gmelinite, which agrees with ledererite in all its 

 physical and crystallographical characters, has shown also an iden- 

 tity in chemical composition. The phosphoric acid detected by Mr. 

 Hayes must be viewed as an accidental constituent, varying pro- 

 bably in different crystals, or in some of them not existing at all. 

 Some of the zeolites, in the Nova Scotia trap, have been found as- 

 sociated with small crystals of phosphate of lime, and it is not impos- 

 sible that some of the minutest of these may have intercrystallized 

 with the ledererite. We regret that we have not been able to ob- 

 tain other specimens to enable Mr. Hayes to give it a re-examination. 

 For comparison, I subjoin the analyses of ledererite and gmelinite. 



Ledererite. Gmelinite. 



Silica 49-47 48*56 



Alumina 21'48 18-05 



Lime 1148 6'13 



Soda 3-94 3'85 



Phosphoric acid . . 3*48 Potash 0-39 



Protoxide of iron .. 0'14 (Ml 



Water 8-58 21'66 



98-56, Hayes. 98*75, Connell. 



* Ann. de Chim. et de Phys. for 1843, t. ix. p. 395. Phillips's Min. p. 627. 



t For the figures see Amer. Journ. of Science, vol. xlvi. p. 234, and vol. 



xlvii. p. 416. Corroborative evidence of the correctness of my opinions 



