90 Mr. Children's Xulicc rcspeciing Dr.Khrenberg'a Collections 



may be expelled from the hydrates of strontia, of which there 

 are two, viz. 



The 9th hydrate, crystallized, composed of 1 eq. strontia 

 + 9 eqs. water = 13^; and the 1st hydrate, pulverulent, 

 composed of 1 eq. strontia + 1 eq. water = 61. 



On considering the compounds that these two metallic ox- 

 ides, barytes and strontia, form with water, some singular facts 

 present themselves to our notice : for instance, the extremely 

 large proportion of water they unite with to form the crystal- 

 lized hydrates, when compared to the hj'drated oxides of all 

 the other metals, to which they seem to form exceptions ; for 

 the law of combination, except with these two oxides, ap- 

 pears to be, ail equivalent q/ water to each equivalent of oxy- 

 gen; thus, the hydrates of potash, lime, nickel, zinc, &c. &c. 

 are composed of 1 eq. of water and 1 eq. of oxygen to 1 of 

 base; the hydrate of the sesquioxide of iron of 3 eqs. of 

 water, 3 of oxygen, and 2 of metal, and the hydrates of the 

 binoxides of tin, vanadium, &c. of 2 eqs, of water, 2 of oxy- 

 gen, and 1 of base. Again, the second hydrate of barytes is 

 the only known instance in which the protoxide of a metal 

 unites with 2 equivalents of water to form a compound of 

 2 eqs. water, 1 oxygen, and 1 base. This earth also resembles 

 the alkalies potash and soda, in retaining water at a red heat; 

 unlike the hydrates of the other earths, lime, strontia, magnesia, 

 &c. which lose the whole of their combined water, and be- 

 come anhydrous, by exposure to an elevated temperature. 

 I am, my dear Sir, your obliged Pupil, 

 St. Thomas's Hospital, J. Denham Smith. 



June 17, 1836. 



XIX. Notice ?-f5/;erfzHgDr. Ehrenberg's Collections of dried 

 Infusoria, and other microscopic Objects. 



To llichard Taylor, Esq., S)-c.Sfc. 

 Dear Sir, British Musciim, 21st June 1836. 



T^R. EHRENBERG of Berlin, well known for his elabo- 

 '-^ rate work on the InJ'usoria* , has recently presented to 

 the British Museum a series of dried microscopic objects, 

 consisting chiefly of infusory animalcules, globules of blood, 

 &c., accompanied by a short notice (too short indeed) of his 

 method of preparing them, and a list of the subjects. Dr. 

 Ehrenberg preserves these most minute and perishable of 

 known organic forms by means of rapid desiccation on little 

 plates of mica, in which manner he informs us that he has suc- 



• Organisrjtion sj/slcinaii/i, Sfc.dcr Infuiions/tiiac/tcn, 3vol=. fol. Dcrlin, 

 1830—1834. 



