PROGRESS OF MICROSCOPICAL SCIENCE. 71 



they float, may now bo considered established upon a firm experi- 

 mental basis." — Transactions of the American Medical Association. 



Diatoms in Hot Water. — It is not a novel discovery to find diatoms 

 in hot water. Still Dr. Blake's recent paper, read before the ' Cali- 

 fornia Academy of Sciences,' is not without interest. He says that 

 the forms were very abundant in water of a temperature of 163° Fahr.,* 

 a small portion of the mud not larger than a pin's head containing 

 many hundred individuals, amongst which could be recognized more 

 than fifty different species. The most interesting point connected 

 with the discovery of these diatoms was their almost perfect identity 

 with the species found in beds of infusorial earth in Utah territory. 

 Most of them were identical with the fossil species described by 

 Ehrenberg, from near Salt Lake, but many were new. He found 

 about fifty-two species, of which thirty are the same as Ehrenberg's, 

 who mentioned about sixty-eight. So close was their identity, that 

 there can be but little doubt that the Utah beds must have been 

 formed in an inland sea, whose temperature was probably about the 

 same as that of the water of the Pueblo spring. The fact that these 

 diatoms can grow in such abundance in water of so high a tempera- 

 ture, affords an explanation of the total absence of every other form 

 of organized beings in the infusorial beds, as such an elevated tem- 

 perature would be totally incompatible with the existence of every 

 other form of living beings. The time at which these infusorial beds 

 were deposited was probably, in the author's opinion, during the 

 Miocene period, as we have evidence that at that period Spitzbergen 

 and other Arctic regions had a temperature of some fifty or sixty 

 degrees above that of their present climate. 



Columnar Dolerite under the Microscope. — At the same meeting of 

 the" California Academy as that above referred to, Dr. Blake showed 

 the advantage of the microscope to the mineralogist. Not being 

 satisfied with the opinion of Mr. Durand regarding a mineral which 

 he found near Black Rock, Nevada, he says : — " I prepared a thin 

 section of one of the crystals, or crystalline prisms, and looked at it 

 through the microscope. This section I now present to the Academy, 

 and even an examination of it with the naked eye suffices to prove 

 that it is a compound rock, made up of heterogeneous substances, 

 imbedded in a dark greenish matrix. With the microscope we detect 

 crystals of augite, nephiline or labradorite, and titanite. I believe 

 the transparent crystals are nephiline ; so perfect is their trans- 

 parency, that at first I concluded that they were holes where the rock 

 had been ground out ; but on using polarized light, I discovered they 

 were doubly refracting crystals. I am not aware that any of these 

 compound rocks have been found in such small prisms. Some of the 

 smaller prisms measure not more than - 10 inch across, and in the 

 specimens I have some three to four inches long. There can be no 

 doubt but that originally they were aggregated into masses, and that 

 their separation is the result of weathering ; in fact, amongst my speci- 

 mens are some in which many prisms are still attached to each other." 



* A hot spring in Pueblo Valley. 



