September 9, 1887.] 



SCIENCE. 



125 



translated into English by Commander Grenfell, R.N., and we are 

 indebted to the courtesy of Captain Piorkowski, Dr. Gruson's repre- 

 sentative in this countr)', for an early copy. The subject and the 

 matter of the work are of exceedingly great importance to a nation 

 which, as is the case with our own, is destitute of the most ordinary 

 means of defence in the event of a foreign attack either by land or 

 sea. So serious is our case, that, as remarked in a private letter 

 from the Admiral of the Navy just received and lying under the 

 hand of the writer, if we desire to learn what advances have oc- 

 curred during the last twenty years, we must go to England, France, 

 Germany, Russia, and even to Constantinople, to study those of the 

 scientitic and mechanical departments of the military and naval 

 establishments, and not to our own army or navy. This work of 

 Dr. Gruson would seem to illustrate such advances in the defence 

 of coasts. 



Dr. Gruson's armor is simply a chilled cast-iron shield, of which 

 the body is a strong normal iron, while the surfaces on the exposed 

 side are chilled like the ' tread ' of an American car-wheel. Such 

 enormous masses are handled, in this case, however, that corre- 

 spondingly enormous chills are needed, and the manufacture of 

 these plates becomes a matter of extraordinary difficulty and cost. 

 All the resources of a great establishment are drawn upon, and all 

 the ingenuity, knowledge, and experience of an able staff are called 

 out in the prosecution of the work. Chilling, as is well known, 

 probably, to most of our readers, consists in the casting of a peculiar 

 quality of cast-iron, known as ' chilling iron,' in contact with a large 

 mass of cold iron forming that part of the mould which is to form 

 the surface to be chilled. The sudden abstraction of heat prevents 

 the isolation of the carbon in graphitic form, as would otherwise 

 occur in the slow process of cooling naturally, and insures its re- 

 tention in the combined form, producing a steel layer of considera- 

 ble depth. The depth so secured is dependent upon the quality of 

 the iron and the efficiency of the ' chill,' as the iron mould is called. 

 The latter must have great thickness and good conducting power 

 to give best results in these applications. Successfully carried out, 

 this process gives a surface harder than tempered steel over a 

 strong and massive interior, the best possible combination, appar- 

 ently, for an armor-plate. 



Dr. Gruson constructs large fixed turrets and land batteries of 

 such plates, and the results of trial indicate them to be more relia- 

 ble defences than any wrought metal, whether iron or steel, or 

 ' compounded,' yet introduced. The weight of these shields is too 

 great for use in naval construction. The first trials were made in 

 1869, at the Tegel range, and it was found that all shots fired 

 against the chilled plates broke into fragments, and that the plates 

 bore the hammering with remarkable success. The experimental 

 committee reported that the chilled armor was well adapted for its 

 use. Later trials confirmed this opinion, and the Prussian govern- 

 ment at once gave directions for its adoption in important lines of 

 frontier defences, and Austria, Italy, and Holland followed its ex- 

 ample. In all these trials the chilled iron shot were found superior, 

 if well made, to any steel shot, except in one or two cases in which 

 makers, like Krupp and the Ternitz company, had either succeeded 

 in securing an exceptional quality of steel, or had found remarkably 

 effective methods of tempering. Plates were tested of from 13.77 

 to 49.21 inches thickness, and were attacked by guns varying from 

 6 to 17 inches calibre, throwing shot weighing from 61 to 2,205 

 pounds. The thickness of plate was usually not far from three times 

 the diameter of the bore of the gun to be resisted. The energy of 

 impact was, in the case of the largest gun, over 47,000 foot-tons ; 

 which was only obtained, however, by firing at short range — 150 

 yards. In all such cases, the shield is subjected to more severe 

 trial than would be likely to be met in actual battle. In trials last 

 year at Spezia, with the 100-ton gun, the shot weighed a ton, and 

 the powder charge 327 pounds, the velocity of impact being over 

 1,700 feet per second. The maximum penetration was four inches, 

 the plates finally breaking up under repeated blows. 



The method of proportioning is to give the plates a maximum 

 thickness in inches equal to from one-fourth to one-third the fourth- 

 root of the energy of the attacking shot measured in foot-tons. 

 The total weight of each plate of which the armor is composed is 

 not far from the weight of the gun expected to be used in the 

 attack. 



The system of defensive armor here described is one in which we 

 have a peculiar interest. We have in the United States, in the 

 ' Salisbury ' and ' Hanging Rock,' and other brands, the best chill- 

 ing irons in the world, and it would seem very possible that this 

 may prove to be the best system for our purpose yet devised. It is 

 especially one which we may hope to obtain permanent advantage 

 from, as it seems probable that its advantages over other forms are 

 not likely to be soon lost. R. H. Thurston. 



MENTAL SCIENCE. 



Heredity of Mental Traits. 



Statistical inquiries have become a recognized instrument of 

 research in mental phenomena. Mr. Francis Gallon has set the 

 pattern in his study of the life-histories of English scientists, in his 

 investigation on the heredity of physical and other traits, in his 

 record of development in childhood, in his researches on visual 

 imagery ; and his composite photography is simply a ' pictorial 

 average.' Students of educational science have adopted the same 

 plan : the contents of children's minds, the record of the daily pro- 

 gress of infants as affected by heredity and by environment, have 

 been registered in almost every civilized country. The increased 

 activity in this direction is sure to bear good fruit. As soon as 

 modern psychology substituted, for the old notion of a single, 

 uniform, typical mind innately endowed with definite faculties and 

 ideas, and uniformly proceeding in definite grooves, the recognition 

 of the endless diversity in every particular of human faculty, it was 

 no longer sufficient to introspect one mind and record the results of 

 your exploration as psychology : one must now use every possible 

 method, study mind from all its many aspects, call in the aid of the 

 psychologist, the pathologist, the educationalist, the anthropologist, 

 and the sociologist, in order to present a picture that shall have the 

 slightest chance of truly representing the reality. That such 

 statistical researches are unusually open to various kinds of falsifi- 

 cation, and are apt to be ' worked ' for more than their worth, 

 every one will admit. It requires great insight as well as caution 

 and patience to draw from a series of answers on mental topics 

 such conclusions as are really warranted without going beyond 

 what the facts logically yield, and again without losing the sug- 

 gestiveness of incomplete records. But all this is an argument, 

 not against the use of such methods, but for the need of more such 

 researches. 



The French Society of Physiological Psychology — an organiza- 

 tion constructed on a much more useful plan than our psychic 

 research societies, and yet including such work as the latter do — 

 have recently issued a circular of inquiry, similar to the ' Record of 

 Family Faculty ' of Mr. Galton. This blank they send only to 

 persons of whose reliability, scientific zeal, and accurate observing 

 powers they have abundant evidence. Each such person fills 

 blanks describing a person with whom he is intimately acquainted, 

 another for his friend's father, and a third for his mother. If he 

 have sufficient knowledge of any other member of the family to 

 answer two-thirds of the questions on the blank concerning him or 

 her, he is to add such information. The person whose traits are 

 described must be at least twenty-five years old, so that his charac- 

 ter has fully matured. It goes without saying that the records 

 will be treated in the most confidential manner. 



The questions are grouped under six heads. I. Education and 

 social position; II. Physical traits; III. Physiological traits; IV. 

 Pathological traits ; V. Moral traits ; and VI. Intellectual traits. 

 The first group asks for one's religion ; his mode of education ; his 

 origin, whether of noble kind, wealthy or poor ; and so on : it out- 

 lines the environment of the individual. Lender the second group 

 are questions regarding height ; weight ; size of head, whether small 

 or large for the height ; shape of forehead ; color of hair and eyes, 

 etc. The physiological questions test the sensibility of the several 

 senses, — of the eye as to near-sightedness, color-blindness, and the 

 like ; of the ear as to fineness ; the development of taste and 

 smell, and so on. They also include the temperament, i.e., nervous, 

 melancholic, sanguine, and phlegmatic ; the diet, whether a drinker 

 of alcoholic liquors, of tea or coffee, and how strongly addicted to 

 them, and the same regarding smoking ; habits of e.xercise, whether 

 regular, violent, and how taken ; general health, whether robust or 



