March 24, 1899.] 



SCIENCE. 



455 



The meeting closed with some remarlvs by 

 Mr. W. Lindgreii, IT. S. Geological Survey, on 

 the Boise Folio (No. 45, of the Geol, Surv.), 

 recently published. 



Wm. F. Morsell. 



DISCUSSIOJS' AND CORRESPONDENCE. 

 ON THE MAKING OF SOLUTIONS. 



To THE Editor of Science : A remark in a 

 recent paper by Professor Macloskie calls my at- 

 tention afresh to a curious error which, so far as 

 I know, is universally current in our zoological 

 laboratories. Professor Macloskie remarks (Sci- 

 ence, Vol. IX., p. 206) " a 1% solution of cane 

 sugar iu water, * * * that is 342 grams, * * * 

 dissolved in 34,200 grams of water." In other 

 words, a 1% solution is made by mixing 1 

 part of the substance to be dissolved with 100 

 parts of the solvent. In this conception the 

 zoologists appear to be at one. It is sufiicient 

 to refer to any of the well-known text-books : 

 Marshall and Hurst, ' Practical Zoology,' 4th 

 ed., p. 464; Gage, 'The Microscope,' 6th ed., 

 p. 179 ; Dodge, ' Elementary Practical Biology,' 

 p. 391. Like many other text-books, Huxley 

 and Martin's 'Practical Biology' (revised ed., 

 p. 496), does not directly commit itself to the 

 error, but gives directions to make the ' normal 

 saline solution' by mixing 7.5 grams of salt with 

 a liter of water. That the normal saline solu- 

 tion is a J% solution is directly stated by Whit- 

 man (' Methods of Research,' etc., edition of 

 1885, p. 207), and Lee (The Microtomist's 

 Vade-mecum, 4th ed., p. 263.), 



These citations abundantly prove that Pro- 

 fessor Macloskie's conception of a 1% solu- 

 tion corresponds with that of other zoologists. 

 If, however, we ask a chemist how such a solu- 

 tion is made, the reply will be : "Dissolve one 

 part of salt, sugar, or whatever the substance 

 may be, in ninety-nine parts of the solvent." 

 And that this is logically correct becomes self- 

 evident upon a moment's thought. A 1% solu- 

 tion of HCl, as all will agree, consists of one 

 part of the acid to ninety-nine parts of water. 

 Why should the fact that in one case we deal 

 with a solid, in the other with a liquid, alter the 

 case? 



It would seem that unless, or until the zoolo- 

 gists come into agreement with the chemists. 



every investigator iu publishing his researches 

 should make a point of preventing ambiguity 

 by stating whether his 1%, hfo, 20% solutions 

 of solids are compounded on the logical or the 

 zoological plan. ^ ^_ Willcox. 



Wellesley College, March 6, 1899. 



THE ORIGIN of nightmare. 



Over and over again when a child I was for 

 years the victim at night of a certain form 

 of mild nightmare, so that it came to be to my 

 fearful imagination no insignificant part of 

 my unpleasant experiences. This nightmare 

 always took the form of a great wave of some- 

 thing gradually rolling towards me and finally 

 engulfing and oppressing me to a painful ex- 

 tent. It would roll up a huge shapeless mass 

 of no particular material, but always irresist- 

 ibly towards me helpless and overwhelmed. 

 Most often it finally appeared to be a huge 

 soft pillow or even formless feather bed, but 

 without color or other qualities save that of 

 engulfing and terrifying. At its worst on vari- 

 ous occasions this mass as it rolled up became 

 a huge fat boar, defined as such, however, only 

 subconsciously, but always dreadful in its power 

 to overwhelm me. All this was years ago. 



One night recently, as I was falling asleep in 

 bed in a lighted room, I became gradually aware 

 of that sensation which compression of a nerve 

 produces, a vague and quite indefinite sense of 

 discomfort localized only in the region about my 

 head and arms, but in my state of somnolence 

 only a growing sensation of discomfort press- 

 ing on my consciousness. Increasing steadily, 

 it finally began to awaken me, and I then 

 became distinctly conscious of the well-remem- 

 bered nightmare of my childhood beginning 

 to approach. With the noise iu the room I was 

 now sufficiently awake to be interested in this fa- 

 miliar visitor, and I lay still deliberately. Grad- 

 ually the mass rolled up towards me exactly as 

 of yore, with no terror in its coming now, until 

 finally it was upon me and all about me op- 

 pressively. I very slightly moved my arm 

 (upon which my head was lying), and the night- 

 mare was for the moment lost sight of in the 

 sensations now localized there. I opened 

 my eyes and instantly the whole experience 

 vanished, closed them and it instantly returned 



