352 



SCIENCE. 



[Vol. XX. No. 516 



be taken to discover if any marked difference exists between the 

 social composition of these groups. While this method may give 

 satisfactory results at a moderate expense, it is far inferior in 

 value to the method of repeated measurements at stated intervals. 

 In this case the same subdivisions must be made, and changes in 

 the social status and in the health of individuals must be recorded 

 and eliminated. In order to carry out such a plan, it would be 

 necessary to organize a bureau with sufficient clerical help to 

 carry on the work. The questions underlying physical and men- 

 tal growth are of fundamental importance for hygiene aud educa- 

 tion, and we hope the time may not be far distant when a work 

 of this character can be undertaken. 



Psaltriparus minimus has a brown crown patch, while P. plum- 

 beus has a lead-colored crown like the back. 



P. lloydi has an ashy crown and black bars on sides of head. 

 This is a southern bird, while the other two may be found as far 

 north as Oregon or Washington. 



SOME ODDITIES IN BIRD-LIFE. 



BT 0. W. SWALLOW, WILLSBURGH, OEBGON. 



It is not my intention, in this article, to describe any new spe- 

 cies that are unknown to ornithologists, but there are many 

 nature-lovers that cannot identify the birds easily; with such, I 

 hope these descriptions may help and create a stronger desire to 

 know more of the birds. 



I will try to describe a few birds that are not as well known 

 to the general observer as the robin, and which, by their rarity 

 or peculiar habits, make them especially interesting to study. 



The first species I will notice is Townsend's Solitaire (Myadestes 

 townsendii). This is a rare bird to me, as I have never secured 

 but one specimen. It may almost be called a hybrid between 

 the thrushes and flycatchers, yet. by its color and flight, it some- 

 what resembles the shrikes. These birds are not as large as the 

 robin, being a more slim bird with longer tail. They measure in 

 inches somewhat as follows: Length, 8.5; extent of wings, 13.5; 

 wing, 4.5; tail, 4.25; tarsus, .75. Their bill is about one-half 

 inch long and strongly resembles the flycatchers, being broad and 

 flat and slightly toothed. Bill and feet are black; the back is 

 brownish ash, or slaty; the breast is lighter, shading into light 

 ash on thecrissum; top of head brownish black, lighter at base 

 of bill ; throat light ash ; alight ring about the eye; wings and 

 tail brownish-blaok ; primary wing-feathers slightly edged with 

 white and the secondary wing-feathers and outer tail-feathers 

 quite extensively white-edged, the primaries and secondaries 

 with a spot of yellow or tawny, giving the wing the appearance 

 of having a bold bar of this color at the point of primary coverts; 

 tail forked and slightly double- rounded. 



This seems to be the only species of the genus found in the 

 United States. They are probably more common between the 

 Eocky and the Cascade ranges ; but stragglers may be found west 

 of the Cascades, even to the Pacific Coast; as I am informed by 

 Mr. R. H. Lawrence that the species has been taken at Astoria. 

 They are reported from New Mexico by A. W. Anthony in the 

 Auk. Dr. Coues gives their range as north to British Columbia, 

 stating that they build on or near the ground, laying bluish- white 

 eggs, spotted with brown. 



The Bushtits {Psaltriparus), although very small, dull-colored 

 birds, are quite interesting and odd, as is also their nest, which 

 is an ingeniously woven, pensile structure that may be found in 

 bushes at the height of one's head, or twenty feet or more up in 

 trees. One that I found last spring was near the end of a long 

 hemlock limb, about twenty feet from the creek over which it 

 Lung. It was securely fastened to the small, slender twigs in 

 three places. It was about nine inches long and four and one- 

 half in diameter, outside. It was well and thickly woven, of 

 moss and cottony substance, being strong enough to hold a num- 

 ber of pounds weight. The entrance was a small hole in one 

 side near the top, and the bottom was well lined with feathers. 

 They lay from six to nine small white eggs. These diminutive 

 birds are only about four Inches in length, with short, rounded 

 wings less than two inches, and a narrow graduated tail some- 

 what longer than the wing. They are of a slate color above, 

 shading into ashy on the under parts. They have no bright 

 colors and are not crested. Bill and feet black. These lively 

 little busybodies keep up a continuous twittering as they flit from 

 twig to twig. There are but a few species found in the United 

 States. 



A DEFINITION OF "SOLUTIONS."' 



BT C. E. LINEBAHGEE, CHICAGO, ILL. 



Within recent years great progress has been made in our 

 knowledge of solutions. This has been in main due to the appli- 

 cation of the laws established for gases to solutions. Solutions 

 are intermediate between liquids and gases. The theory of gases 

 has been well developed, and the next problem is to devise a gen- 

 eral theory of liquids. There are two ways of getting at the na- 

 ture of liquids, — through the critical point and through solu- 

 tions. Pellat ^ has recently shown the need of pnecision in the 

 definition of the critical point, and has deduced from a considera- 

 tion of the iso-thermal curves of carbon dioxide determined by 

 Andrews ^ a definition at once concise and precise. It is my 

 intention in this paper to subject to examination the existing 

 definitions of solutions, and, if they be found inadequate or in- 

 accurate, to propose another. Definitions, the preliminaries of 

 science, are but landmarks of classification As scientific knowl- 

 edge advances, the classifications and definitions change: they 

 are provisional and progressive. Until within a few years, our 

 notions of the nature of solutions were so vague that it was not 

 possible to insist upon precise definitions; but now that we 

 have a theory of solutions that rivals the theory of gases in sim- 

 plicity and even surpasses it in the accuracy of its experimental 

 results, it is time that a suitable definition be adopted. 



Among the formal definitions of solutions (which are not very 

 numerous) of acknowledged authorities, I will quote for the sake 

 of comparison the following: — 



(a) " Auflosung heisst, wenn sich ein fester Korper rait einer 

 Fliissigkeit (einem tropfbar-fliissigen Korper) so verbindet, dass er 

 in dieser Verbindung flussig wird. . . . Die Fliissigkeit nennt 

 man dann das Losungsmittel, der vorher teste Korper heisst auf- 

 gelost, und die neue Verbindung eine Auflosung " (Berzelius, 

 Lehrbuch der Chemie, I., 424, fifth edition). 



(6) " The liquefaction of a solid or gaseous body by contact with 

 a liquid, the solid or gas being diffused uniformly through the 

 liquid and not separating when left at rest " (Watts' Dictionary 

 of Chemistry, article Solutions). 



(c) "Losungen sind homogene Geraenge, welche man durch 

 mechanische Mittel nicht in ihre Bestandteile sondern kann " 

 (Ostwald, Lehrbuch der allgemeinen Chemie, I., 606). 



In these typical definitions there are three questions that re- 

 quire examination: (1) What is the state of aggregation of solu- 

 tions? (2) Is homogeneity necessarily a characteristic of solu- 

 tions alone ? (3) What is to he understood by mechanical means, 

 and is it true that solutions cannot be decomposed into their con- 

 stituents by such means 1 



As to the first question, it is seen that the two first definitions 

 regard a solution as liquid, which is, indeed, the common con- 

 ception. Yet undoubtedly solids have the power of dissolving 

 one another under certain conditions, so that a solution may be 

 solid.* The expressions " solutions of gases in gases," of "liquids 

 in gases." and even of "solids in gases " are quite general and 

 used by good authorities. Thus the state of aggregation of solu- 

 tions may be gaseous, liquid, or solid. (See, however, the defini- 

 tion proposed below). 



But are there not homogeneous mixtures that are not solutions, 

 no regard being had, however, to mixtures of powders, etc.? 

 Every one knows what solutions of cry.stalloids, such as sugar or 



1 By solution is understood in this paper tlie ready-made mixture, no ref- 

 erence being had to its mode of formation; for the action of the solvent upon 

 the substance to be dissolved as well as the product of the action is commonly 

 called a " solution." 



= De la Deflnitlon et de la Determination du Point Critique, Jour, de Phys. 

 (3). I., 225. 



8 Phil. Trans. II. 1869. 



* Van't Ho£f. Zeltschrift fur physikaiische chemie, 5., 323. 



