Vol. XXIII. No. 3.] 



POPULAR SCIETSTCE ITEWS. 



35 



knowledge of a subject will not make an expert; he 

 must know how to apply his knowledge. The man 

 who has the most knowledge is not always the best 

 expert. But it is he who knows just what he can 

 do with the knowledge that he has, who is willing 

 to say that he does not know, when he is in doubt, 

 and who tells the truth, even when it is against his 

 client, that succeeds best. Every expert must have 

 more or less knowledge of the law, especially of 

 that portion of it that relates to the rules governing 

 evidence. He finds that he is constantly called upon 

 by lawyers for advice concerning their cases, and 

 that the evidence that he gives in court is often the 

 smallest portion of his work. He is expected by 

 his employers to constantly watch the progress of 

 the case, and assist in the examination and cross- 

 examination of witnesses.. The late Judge Lord 

 was asked at one time to define the difference be- 

 tween lawyers and experts. He is said to have re- 

 plied that he did not know of any except that " the 

 experts were sworn not to lie and the lawyers were 

 not so sworn." Lawyers, however, as a rule are 

 not good witnesses ; it makes considerable ditference 

 to them whether they are the victims on the witness 

 stand, or whether they are engaged in torturing said 

 victim. 



Complaints are very frequently made that experts 

 of the same standing frequently differ very widely 

 in their views of the same set of facts. This very 

 often arises from the much broader view taken by 

 one than is taken by the other. As an instance, a 

 few months ago a cream of tartar substitute was 

 given to the chemists to analyze, and they were 

 asked to report on its composition and the method 

 by which it was made. The two analyses substan- 

 tially agreed. As to the method of manufacture 

 there was a wide divergence. Made according to 

 the method given by A, it would cost more than 

 double what it would if made by the method given 

 by B. In this case, a word or two from B would 

 have placed A on the right track and the reports 

 would have been alike. Generally the expert for 

 the defence has greatly the advantage in court. Ev- 

 idence for the prosecution or the plaintiff must be 

 positive in character, while for the defence it is 

 often sufficient to raise doubts in the mind of the 

 court. The following will illustrate this : In a case 

 some years ago a witness testified very positively to 

 finding some particles of decaying meat in a source 

 of water supply, and he drew the conclusion from 

 this that the water would be unfit to drink. On 

 cross examination he was asked the question, " Did 

 you ever eat a game dinner?" A question that 

 seemed to the lawyer who asked it, and to the court 

 as totally irrelevant to the point at^issue. But the 

 next question was, " Is there not more decaying 

 animal matter in a single piece of game, than in a 

 hundred gallons of this water.'" The reply, given 

 after much hesitation, was, " that there probably 

 was." In this case, nothing that the witness had 

 said on the direct examination was contradicted, 

 but his testimony was as effectually answered as if 

 half a dozen witnesses had testified to the harmless 

 nature of the decaying flesh. The proper reply to 

 the last question would have been that the presence 

 of decaying flesh was not to be feared so much from 

 itself, as that it furnished food for germs that might 

 prove very injurious, but he had committed himself 

 too thoroughly to the theory that it was the flesh 

 itself that was injurious, to get out of the fix in that 

 way. As a general rule, an expert soon learns to 

 be verv cautious until he finds out very fully the 

 facts in a case. He is also apt to answer all ques- 

 tions in a guarded manner. I recollect once hear- 

 ing a lawyer remark, " Here is an expert who 

 answers ' No' to a question." 

 One very common fault of experts is attempting 



to show off on the witness stand. Woe to the one 

 who attempts this, and who happens to fall into the 

 hands of a smart lawyer who knows just how to 

 manage such a case. In fact, nine-tenths of the 

 complaints of the treatment of scientific men by 

 lawyers have arisen from this one cause. It takes 

 just as much training to make a good witness as it 

 takes to make a good lawyer, and when a professor 

 fresh froiTi the class-room is put on the stand for 

 the first time, he is very apt to be troubled with 

 stage fright. The lawyers are quick to see this and 

 to take advantage of it. The consequence is that 

 he leaves the court room vowing that he will never 

 be caught in such a position again. And he rushes 

 off to some scientific journal with an article against 

 lawyers in general, and declares that the whole sys- 

 tem of taking evidence is wrong. An experience 

 of many years in all courts in which evidence is 

 taken in this country, from the police court to the 

 Circuit court of the United States, enables me to 

 sav that the expert who knows his business and 

 who sticks to his text, will rarely meet with any 

 but the most gentlemanly treatment. While the 

 man who goes into court with the idea that the sun 

 rises and sets somewhere in his immediate vicinity, 

 is apt to retire with the feeling that perhaps he does 

 not know everything. 



It must not for a moment be supposed that there 

 are not charlatans and quacks in this as in every 

 other profession ; unfortunately, they, like the poor, 

 are always with us. But the proportion i^s not 

 greater than in other professions. It is often urged 

 as a reproach against experts, that you can find an 

 expert to testify on any side of any question. In 

 reply to this I can only say there are very few ques- 

 tions which have not two perfectly good sides. 



Take for instance a milk case. One expert testi- 

 fies that a certain sample of milk that he has ex- 

 amined contains only ten and a half per cent, of 

 milk solids; that good milk should contain thirteen 

 percent, and that he has never known of a case 

 where the solids were as low as this. His opponent 

 comes on to the stand and admits that this is very 

 poor milk, but he cites one or two cases that have 

 come to his notice in which the milk was as poor as 

 this, and in which there could be no doubt in re- 

 gard to the purity of the milk. This is generally 

 sufficient in the absence of a special statute to clear 

 the defendant. Expert No. 2 by no means says that 

 the milk is not watered ; the trouble is that, with all 

 the facts before him, the first expert cannot swear 

 that it is only a matter of opinion. To meet this 

 state of the case, many of the States have passed 

 special acts declaring that all milk that is below a 

 certain standard shall be considered as adulterated. 



One common fault among expert witnesses is the 

 use of too many technical words. The doctor who 

 observes to the court that he found a man suflTering 

 with a contusion immediately over his left optic, 

 may be correct, but he will be better understood by 

 the jury if he says the man had a black eye. He 

 must always recollect that the language which he 

 uses in his every day work, is no more intelligible to 

 the ordinary mind than so much Greek or Latin. 

 As a general thing the expert is listened to with the 

 greatest attention, the Judge often interrupting him 

 in order that he may explain certain points more 

 fully. To sum up, the profession of an expert is an 

 extremely important one, but it is also one in which 

 unprincipled men with a smattering of knowledge 

 may do great damage. It has been proposed that 

 no one should be allowed to practise the profession 

 without a permit from the court. But it would be 

 ! difficult to pass on the qualifications of an expert, 

 for no two cases which arise in court are exactly 

 alike. Thus we have experts in writing, chemical 

 and medical experts, experts in electrical matters, 



and in mechanics and physics, no two men cover- 

 ing exactly the same ground. 



The expert witness is always expected to " quali- 

 fy before he testifies" in a case, but this is generally 

 a mere matter of form, and very rarely is his testi- 

 mony rejected on the ground that he is not qualified, 

 his qualification being a matter for the jury to pass 

 upon. In one case that I know of, a man who is 

 densely ignorant in regard to the most common 

 principles of chemistry, has been allowed to try to 

 pervert the cause of justice for years, simply be- 

 cause there is no ready method of reaching such a 

 case. 



Time, however, cures all such cases, and as they 

 rarely are employed by the prosecution they do not 

 do a very great amount of damage. If the govern- 

 ment cannot prove its case against such testimony, 

 it has not a very strong cause. King Solomon evi- 

 dently had just such a character in mind, when he 

 gave his celebrated advice in regard to answering 

 fools. S. 



A NEW PRIMARY BATTERY. 



It is well known that batteries, in which two 

 fluids are employed, labor under difficulties intro- 

 duced by the porous cup usually employed. The 

 cup is resorted to for the purpose of separating the 

 two liquids, while aftbrding a passage for the cur- 

 rent and a path for the electrolytic action. If the 

 cup be made too porous the liquids will dift'use too 

 easily, and cause wasteful local action ; while if it 

 be made but slightly porous to prevent this very 

 difficulty, the internal resistance of the cup and bat- 

 tery will become very great, and thus reduce its 

 efficiency. In order to overcome these difficulties, 

 the Electrical World informs us that Mr. J. L. 

 Roberts and Mr. Harry L. Brevoort, of New York, 

 have for .some time past been engaged in a series'of 

 experiments, the results of which are embodied in 

 the battery now made by them, and the nature of 

 which calls for some notice. Messrs. Roberts and 

 Brevoort, recognizing the troubles and problems 

 above mentioned, started out to make the partition 

 separating the two liquids in a battery of a material 

 which should practically be non-porous, but with 

 electrolytic properties, so that whether the battery 

 be on an open circuit or closed, the liquid, as such, 

 on one side of the partition would not interfere or 

 intermingle with the liquid on the other side of the 

 partition, or only to a very limited extent : but when 

 the circuit is closed, and the battery is called upon 

 to give a current of electricity, chemical action 

 could take place through the partition. This prop- 

 erty in a partition has been secured by the use of a 

 number of materials. Among those first tried were 

 gelatinous or jelly-like materials, such as boiled 

 starch, which was confined between walls of cloth, 

 so as to make a suitable diaphragm ; and other veg- 

 etable and animal substances of a similar nature 

 have been used. In the most recent form the in- 

 ventors employ mineral substances of a gelatinous 

 nature, and among others they tried the gelatinous 

 silicate of soda, with which they impregnate the 

 ordinary porous cup. The action of this diaphragm 

 or partition the inventors explain as follows : — The 

 diaphragm or partition is a non-porous substan- 

 tially-solid homogeneous wall, whose particles, 

 while sufficiently solid and compact to maintain 

 their compositions, and so prevent, for practical 

 purposes, any transmission of fluid through them, 

 are yet themselves able to act as electrolytes, and 

 suffer such decompositions and re-combinations as 

 are essential to the electrolytic transmissions of 

 electric force. In other words, they have in the 

 partition combined in the one substance the solid 

 properties of the earthenware and the electrolytic 

 properties of the liquid, or, as they say, they have 



