National Academy of Sciences. 



11 



That is, if you were to talro those seven substances and 

 separate eacli into its ultimate constituents, you would 

 find each giving not only the same materials to ultimate 

 analysis, but weight for weight the same amounts of 

 these, materials; and yet each of the seven substances is 

 intrinsically different from thj other in its character, 

 appearance, and chemical reactions; and no one of them 

 can be transformed mro the other. In the whole realm 

 or' inorganic chemistry there has been no similar 

 instance recorded, although among organic bodies there 

 are not- a few such cases. 



The substance with which the series begins was dis- 

 covered by Dr. Eidmami. It is an exceedingly stable 

 compound. Its constituents are two parts of cobalt, six 

 of ammonia, and six of uicric oxide. Its chemical 1'or- 

 ni ula is: 



Co 2 (N II 3) 6 (N O 2) 6. 



The six other bodies metameric with it, were obtained 

 by Prof. Gibus by making the compounds and combining 

 them when made, in the manner indicated in the nota- 

 tion which follows. It will be observed by the chemist 

 that the combination of the compounds is that of an 

 acid with a base, in each instance making a true salt, 

 obtained in crystalline form. For the "sake of abridge- 

 ment in notation, in what follows, the ammonia (N H 3) 

 is represented by A and the nitric aci I by X. Oa ac- 

 count of the difference in their atomic constitution. Dr. 

 Cibbs divides the seven substances iuto three series. 



First series Eidmann's discovery: 



Co2 A6XG 



Second series Dr. Uibbs's discovery: 



(Co 2 A 4 X S) 



II 



II 



II 



2. Co 2 A 6 X 6 



3. Co 2 A 6 X 6 

 4.. Co 2 A 6 X 6 



(Co 2 A 8 X 4) = 

 IV 



(Co 2 A 4X8)2 (Co 2 A 10X2) = 



II IV 



(Co2A4XS)3 (Co 2 A 12) = 



Tliird series Dr. Gibbs's diaciiverv: 



VI VI 



(Co 2 X 12) ^ (Co 2 A 12) = 



(Co 2 X 12) (Co 2 A 8 X 4)3 = 



(Co 2 X 12)2 (Co 2 A 10 X 2)3 = 



As each of the salts thus obtained is beautifully crys- 

 talline and perfectly well defined, and each salt of the 

 second and third groups gives the icactions of each con- 

 stituent with perfect distmctnsss, uo doubt cau exist as 

 to their real chemical structure. 



2. Co 2 A 6 X 6 

 4. Co 2 A 6 X G 

 6. Co 2 A G X 6 



COMPARATIVE VELOCITY OF LIGHT LIST A1E 

 AND IN VACUO. 



BY PROF. STEPHEN ALEXANDER OP PRINCETON COL- 

 LEGE. 



This brief paper merely contained a few 

 interesting suggestions on a small correction of the 

 velocity of light as deduced from experiment. 



In accordance with the und ula tory theory the velocity 

 of light must be less in atmoopheric air than invacuo, 

 in the inverse ratio of the index of refraction of 

 atmosuheri 1 ; air to 1: that is. as 1 to 1.000291. The 

 velocity theu as ascertained by experiment under the 

 air should be increased by just about 0.003294 of itself to 

 be equal to that in vacno; i.e., to the extent, almost 

 exactly, of 5o miles per second ; a very small quantity 

 indeed in comparison with the whole velocity of 183,000 

 miles per second ; and yet small as it is and so small as 

 to be below the limits of error of the experiments in 

 question it is yet very closely equal to three times the 

 velocity of the earth in its orbit. 



It is an outstanding excess, and no more, with which 

 we oft:-u have to do. as, for example, in the measure- 

 ment of temperature; but the scale on which those dif- 

 ferences sometimes present themselves makes them, _ 

 email as they aiay be m their original comparison, graud I of our public domain. 



In comparison with ordinary standards. Prof. Alexan- 

 der was not aware that anything has yet been put for- 

 ward elsewhere on this subject. 



Prof. Bilgard remarked that the postulate of ttm 

 paper that the utulululory theory iv<|iiiird tliat 

 light must move more slowly in air than in vacuo, 

 was not by any means settled. Them had been an 

 approximate experiment on aberration, by Prof. 

 Airy, who filled a telescope with water and sent, 

 light through it but n- deviation w.is observed 

 after the- most careful observations. We aro not 

 sufficiently acquainted with the clu.raehr and 

 properties of the luminif orous ether to speak with 

 certainty on these subjects, but the investigation i. 

 well worthy of the highest effort. Prof. Il-nry 

 spoke a few words of merited praise about the com- 

 munication. 



RECENT WORK OF PROF. HAYDEN. 



SUPPLEMENTARY TO TRIRUNE ACCOUNTS OK EXPLOR- 

 ING EXPEDITIONS AT THE WEST. 



Prof. F. V. Hayden appeared before tlie Academy 

 to give a general account of the scientific explorations 

 and survey at the West in which he has bseu en- 

 gaged. As full accounts of these explorations have 

 appeared in THE TRIBUNE it will be unnecessary to 

 reproduce the details with which our readers aro 

 already familiar. The following particulars are 

 concerning more recent work and bring the story of 

 these explorations from the accounts in Tin-: Tiua- 

 UNE Extra of Dec. 30th to the date of the meeting. 



The party returned from the fl dd-work in Colorado 

 in October and at once commenced the prcparati"ii 

 of the annual report and the construction of the maps. 

 The seventh annual report, containing the preliminary 

 results of the survey for 1873. will be readv for presenta- 

 tion to Congress in May, and will form an octavo 

 volume of about 800 pages, with over 301) illustrations, 

 sections, profiles, maps, &3. Tue geological and rum- 

 eralogical, as well as topographical, structure of the 

 remarkable mountain region of Colorado hits been 

 worked out with care; sections of all the 

 mines have been made with the utmost at- 

 tainable accuracy, showing the connection of 

 the mineral lode with the country rock, so that 

 the light which will be thrown upon the origin and hi--- 

 tory of tlieso formations will be of great value to 

 science. T\vo classes of map*, on a S'.'alo of four miles to 

 one inch, have been prepared. The first class are in con- 

 tour lines of 230 feet, upon which to represent the vari- 

 ous geological formations in the areas explored, with 

 suitable colors. On the second class the peculiar moun- 

 tain forms will be delineated, in excellent relief, by a 

 peculiar kind of brush-work. T.i :* ;uv the topograph- 

 ical maps. When the survey of Colorado is completed 

 the great features of the physical history of 

 that Territory will be summed up in one volume, with 

 iin atlasof maps and sections. Prof. Ilavd'-n regarded 

 this work as a contribution from the General Govern- 

 ment to Its ward, the Territory, toward the development 

 of its resources. It will also form the i>a>u upon which 

 more detailed surveys can be carried on by th" eniiimii' 

 nity itself. Dr. Ilnyd'en closed with an app -al to tin- nn-iu 

 of the National Academy to spare no etlort to enlist 

 the continued sympathy of Congress in the great \\oi!; 

 of making known to the world the unexplored portions 



