a 6 



SCIENCE. 



[Vol. XV. No. 361 



-cream-of-tartar, and one made by substituting calcium acid phos- 

 phate for the cream-of-tartar, two different amounts of Rochelle 



-salts and calcium acid phosphate were used, and each subjected to 

 the same conditions. 



The difference in the retarding action of these residues is easily 



■seen from the following table (digestion carried on five hours) : — 



The superiority of cream-of-tartar over calcium acid phosphate 

 as the acid principle of a baking-powder is shown very well in this 

 last experiment ; and, although it is claimed that the latter form of 

 powder furnishes the necessary phosphates for building up the 

 bone-tissue of the body, yet this benefit is rather overbalanced by 

 ■the harm done by the retardation of the digestive process. 



In some cases where it was desirable to compare the effects of 

 'tvyo baking-powders directly, or in cases where insoluble salts were 

 ■used, time digestions were resorted to, in order to avoid loss in 

 neutralizing and filtering. 



For these experiments 20 grams of coagulated albumen, and 200 

 -cubic centimetres of artificial gastric juice, were employed. 



The digestions were carried on in a 40° C. water-bath, stirred 

 -well, and observations made regarding the time of disappearance 

 -of the coagulated albumen in each digestion. 



In the first series, three amounts of a phosphate baking-powder 

 ■were used, and, as in previous experiments, a control free from 

 powder. 



Having obtained the datum in a previous experiment that a 

 phospate powder adulterated with alum had great retarding action 

 on digestion, a comparison was made between a pure phosphate 

 powder and one known to contain alum ; and, although the di- 

 gestion was not carried on until all of the coagulated albumen had 

 disappeared, yet it was carried far enough to enable the observer to 

 make a good comparison. No. i contained no salt; No. 2, .5 of 

 a gram of pure phosphate powder; No. 3, i gram; No. 4, 1.5 

 grams ; No. 5, .5 of a gram of impure phosphate powder ; No. 6, 

 I gram ; No. 7, 1.5 grams. 



The albumen in No. i was first to disappear, followed closely 

 by No. 2, then a little later by No. 5 ; and so on, in every case the 

 one containing the pure phosphate powder digesting before the 

 one containing a similar amount of impure powder. 



Ammonium carbonate has been put down by some as inhibiting 



■ digestion, but others claim that on baking it volatilizes and goes 



■ off as ammonia gas, leaving a harmless residue; but, in fact, only 

 a small portion of the whole is driven off in this way, for the 



.ammonia forms a compound of ammonium tartrate immediately on 

 ■' heating, and this latter salt is not easily decomposed by heat. 



To discover the relative inhibitory action of this residue on di- 

 gestion, a series was made, using comparative amounts of alumin- 

 ium phosphate, Rochelle salts, and ammonium tartrate. No. i 

 contained no salt; No. 2, .5 of a gram of aluminium phosphate; 

 ;No. 3, I gram ; No. 4, .5 of a gram of Rochelle salts ; No. 5, i 

 ;gram ; No. 6, .5 of a gram of ammonium tartrate; No. 7, I 

 rgram. 

 . No. I was digested in about 45 hours, followed closely by No. 



6, and the remaining ones digested in the following order : Nos. 



4,7. 5.2,3- 



As far as could be seen from this series, there is very little dif- 

 ference in the inhibitory powers of the Rochelle salts and the 

 ammonium tartrate ; and the latter cannot be considered, therefore, 

 to be more harmful than the residue of a pure baking-powder. 



As a summary of the facts brought out by this investigation, we 

 find (i) that the residues of all baking-powders, no matter how 

 pure may be their constituents, have a harmful effect on digestion, 

 due, in all probability, primarily to the fact that the salts are acted 

 upon by the hydrochloric acid of the gastric juice with the forma- 

 tion of more soluble compounds, and, secondarily, that these salts 

 may form organic compounds with albuminous bodies in the 

 same manner as many of the metals do ; (2) that calcium phosphate, 

 on account of its great inhibitory action on digestion, must be re- 

 garded as a poor agent for the manufacture of a baking-powder, 

 while ammonium tartrate may be looked upon with more favor ; 

 (3) that the presence of alum in a powder made with calcium 

 phosphate greatly increases its retarding action ; (4) that the least 

 harmful baking-powder is one containing only the bicarbonate of 

 soda and cream-of-tartar, and that the presence of any other 

 chemical substance, however harmless it may be in itself, tends 

 only to increase the complexity of the residue and impair the ac- 

 tivity of the gastric juice. R. TAYLOR WHEELER. 



Jersey City, N.J,, Dec. 24. 



Resemblance of People. 



While in Chicago during the Republican convention of the 

 summer of 1888, it occurred to me to make an estimate of the num- 

 ber of people that must be taken, in order that there may be in gen- 

 eral two persons who look enough alike for the resemblance to be 

 noticed at first glance, taking account only of the features, and not 

 of characteristics of voice, motion, etc., which of course help us 

 very much to distinguish persons. 



Posting myself upon a street-corner so as to face the moving 

 crowds of people, and throwing myself into as passive a condition 

 as possible, I gazed intently upon the passing faces. Out of 700 

 persons tried, 29 brought to mind some acquaintaince. I esti- 

 mated the number of available acquaintances at 5,000 at least, for 

 among the number suggested some could scarcely be called ac- 

 quaintances. This would indicate, that, among 120,000 people, 

 one will likely be found to resemble any one person enough to be 

 noticed at a glance; or among )■' 120,000, i.e., about 400 persons, two 

 will probably be found to resemble enough to be noticed at a glance. 

 Of course, the result depends upon one's memory of faces and the 

 ease with which faces are distinguished, and undoubtedly upon 

 many other things. W. S. Franklin. 



Lawrence, Kan., Dec. 23.' 



A Remarkable Bo'wIder of Nephrite or Jade. 



The writer lately obtained in southern Oregon a bowlder of 

 jade, which is the largest erratic mass of the mineral yet found on 

 this continent. It was found among the auriferous gravel of a 

 stream near a small mining hamlet by a gold prospector. Its 

 color is of a mottled deep leek green, interspersed with veins of 

 light green and yellow. It is turtle-back in form, and weighs 47i 

 pounds avoirdupois. To the eye it is semi-translucent, splintery, 

 and fibrous in its structure ; but that it is remarkably compact and 

 homogeneous in character, is attested by a blow, when it produces 

 a clear metallic ring like bell-metal. The specific gravity of three 

 small chips taken from different parts of the bowlder is 2.949, 3.01, 

 3.04, the difference being probably due to the variance of magnetite 

 in the pieces. The extremes correspond nearly with those given 

 byVr. Fischer (Nep/irzY 2aid Jadeit, p. 54, Stuttgart, 1880) and by 

 Clarke (Proceedings of the United States National Museum, p. 

 116, 1888). This occurrence of nephrite bowlders among the river- 

 gravel of our Western coast streams, in connection with Mr. G. M. 

 Dawson's {Science, xi. p. 186), tends to confirm the belief that it was 

 found by the native races of that coast in sufficient quantities from 

 which to manufacture their various implements of jade. 



James Terry. 



New York, Dec. 30. 



