10 



Tribune Extras Lecture and Letter Series. 



name originally given to tlie whole series of plateaus- 

 Colorado plateau. 



These plateaus cau be thrown into classes on ecologi- 

 cal grounds, as follows: The tertiary plateaus to the 

 north, cretaceous plateaus immediately south, trias^ic 

 plateaus next m order, and carboniferous on the south. 

 The geological classification serves well, also, tor geo- 

 graphic purposes, as each group has peculiar topographic 

 features, depending on the texture and structure of the 

 roots of which they are composed. 



A VARIETY OF SUBJECTS-TniRD DAT. 



AN INSTANCE WHERE SOLAR TIDES KXCEIvD THOSE 

 CAUSED UY THE MOON A NOVELTY IN INORGANIC 

 CHEMISTKY 1IIE THEORY OF CYCLONES NEARLY 

 ALL THE ATMOSPHERE OF THE EARTH TWO HUGE 

 CYCLONIC WHIRLS. 



WASHINGTON, April 23. Disagreeable -weather 

 tended to reduce the audience of April 23 at the 

 Smithsonian Institution. The subjects discussed 

 did not equal in general interest those of the previous 

 day, hut they had at least the merit of bringing 

 forwaid some novelties in scientific discovery. The 

 statements of Prof. Ferrel respecting the tides of 

 Tahiti were cm ions rather than important. The 

 discoveries of 1'rof. Gibb.sof Harvard, who is equally 

 noted as an original investigator, and as an editor of 

 The American Journal of /Science and Arts, of com- 

 pounds in inorganic chemistry having the character- 

 istic of metamerism thathas hitherto been unknown 

 except among organic substances, seems to open a 

 new iield of research. Prof. Gibbs mentioned that 

 lie had given no name to his new compounds; for 

 which we may be truly thankful, since names that 

 chemists are apt to indulge in when making discov- 

 eries in organic chemistry, are rarely limited by six 

 or eeven syllables and sometimes reach a dozen. 



The communication from Prof. Alexander, the dis- 

 tinguished astronomer of Princeton, suggests a very 

 interesting though difficult inquiry. Prof. Hayden 

 gave a glowing and rapid sketch of the explorations 

 in which he has been engaged, and of the work 

 accomplished and under way. He was warmly 

 greeted by several of the professors, who evidently 

 held liis work in high esteem. Prof. Silliman 

 told of the localities of the American ores of 

 tellurium that curious substance which once on 

 a time a bold experimenter swallowed, the result 

 being that his friends dropped oil' gradually. He 

 noticed after a few days that everybody seemed to 

 avoid him. Finally he cornered one of them and 

 begged an explanation. " Why, the fact is," said 

 his friend, with his nose in his handkerchief as ho 

 spoke, "yon must be aware that you have u horii Me 

 Binell." '1 he experimenter was obliged to retire into 

 obscuiity for some weeks, till the tellurium was out 

 of his system. 1'mf. I'd \> Ts theory of the law of 

 cyclones was exceedingly interesting to the meteor- 

 ologists present. 



THE TIDES OF TAHITI. 



3Y PROF. WM. FERREL OF THE U. S. COAST SURVEY. 



In 1858 the U. S. Coast Survey took advan- 

 tage of the surveying expedition under charge of Capt. 

 (now Commodore) John Rodgn-sto obtain a series of 

 tidal observations at the Island of T iliiti in 1 he Pacific. 

 A soil-registering tide gau^e was sent by the Coast 

 Survey, and left by the expedition in tho hands of a 

 French soldier at tap town of Papeetee on that island. 

 By this means a series of observations nearly complete 

 was obtained from June 1 to Ojt. 1. These were re- 

 duced by the Coast Survey and published m the report 

 of 1SG4. The great peculiarity of these tides 

 is that the solar tide is for tho most part 

 greater than tho lunar tide, although the force pro- 

 ducing the latter is more than double that producing 

 the former. There is only one other case, of the sort in 

 the world at Courtown, Ireland. It is not, however, 

 due to any exception in tho general theory of the tides. 

 Certain constants iu the tinal expressions, which have 

 to be determined by observations, are unusually large 

 in this case. It is yet impossible to specify, however, 

 what are the irregularities of ocean bottom and of coast 

 outline which occasion the phenomena lu thij particular 

 instance. 



A representation was here given by diagrams of the 

 solitidal intervals ; i. e., a mean of the curves for morning 

 and evening tides, as furnished iu the Coast Survey Ra- 

 port. The small diurnal tide was eliminated from the 

 representation, which only gave the semi-diurnal tides. 

 The sou' tidal intervals were given instead of the luui- 

 tidal. because the former were the larger. In Jane, 

 however, at the time of the quadratures, when the solar 

 and lunar forces are in opposition, the sun has 

 its greatest declination, and tho moon is near 

 the equator, and hence the solar tide is smaller 

 and the lunar greater than usual. Hence 

 also, iu Ji-ue and July, tho times of hitrh 

 water at tlio quadratures follow the moon, and tho 

 range of the solitidal interval is from to 12 hours. But 

 toward September, at tho quadrat u<vs tho moon is 

 near its maximum declination and I ho sun near the 

 equator, and hence the solar tide is lartr/r than usual 

 and tho lunar smaller; and tlie times of hiirh water fol- 

 low the sun rather thau the moon, and occur within a 

 ranee of three or four hours near nm>:i and midnight. 



From theoretical considerations applied to the observa- 

 tions, it was, however, shown that tin- observed times of 

 hiirh water in the small tides, aff-cted by abnormal dis- 

 turbances of the winds and changes of barometric pres- 

 sure, necessarily differ considerably from the theoretical 

 calculaiion. which merely depends ou the lorces excr- 

 ciccd by the sun and moon. 



i 



METAMERISM IN INORGANIC CHEMISTRY. 



1JY IM.'OI'. WOI.COTT GIBBS OF HARVARD UXIVKRSITY. 



Although this paper was o a technical char- 

 acter, audits greatest value is of course to those who 

 are interested directly in chemu-al researches, it pre- 

 sents a discovery so novel in its elur.ieier that it cau 

 scarcely !>; without interest even to I lie non-professional 

 Miidenl. Hitherto what has been deiMUiiin ited metame- 

 rism has never been observed cxeept in oriranio 

 substances. Bodies are said to be metumeric when they 

 are of the same composition and atomic weight, but dif- 

 fering entirely in their properties, iu c.mseqivMico of dif 

 ferent molecular constitution. Prof. Gibbs has discov- 

 . Ted six such bodies bearmjr such a relation to one an- 

 other and to a seventh whicli was not of his discovery. 



