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These lenses represented the ultimate in aerialsurvey lenses until the Zeiss "Topogon" f/6.3lens (Fig. 8c), covering a half angle of 450 wasdesigned by Richter in 1933. A 6-inch lens of thistype covers successfully to the corners of a 9 X 9-inch picture. It is also made in this country byBausch and Lomb, as the "Metrogon" lens. Asample in the 12-inch size has been made to coveran 18-inch square picture, but this very largesize seems likely not to be used extensively be-cause of the size and weight of the camera, andthe difficulties of handling this large film. Ross inEngland have made a slight modification of theTopogon lens, known as the f/5.6 Wide-angleSurvey lens, by dividing the rear positive elementinto two airspaced elements.

As can be seen from the diagram in Fig. 8, theTopogon lens is of an extreme meniscus type ofconstruction, being probably descended fromthe old Harrison "Globe lens," or the Busch"Pantoskop," making use of the teaching givenus by Von HJegh in the Goerz Hypergon. The

MARCI, 1942

deep meniscus form of the Hypergon leads to aperfectly flat field out to 670 from the lens axis,but as it is uncorrected for chromatic andspherical aberration, its useful aperture is limitedto about f30 or less. The Pantoskop wasachromatic but not spherically corrected, itsaperture being likewise limited to aboutf/30. InRichter's design he has separated the positiveand negative elements of the Pantoskop lens, andgiven the negative elements a "bending" to adeeper meniscus shape. In this way, sufficientdegrees of freedom are made available to correctthe aberrations atf/6, over a semi-field of about450. At this very wide angle, the illumination isnaturally rather low, but the lens is quitesatisfactory in practice.

A high lens speed is of almost no importance tothe peace-time mapping photographer, becausehe flies only in perfect weather. However, extremeangular fields are very desirable, and now that a450 field is available, he will never be satisfiedwith less.

J. 0. S. A. VOLUME 32

Optics in Sabotage and Espionage*

WALTER G. DRISCOLLFederal Bureau of Investigation, Washington, D. C.

THE maintenance of our national defense andT the preservation of our internal securityhave increased the quantity of work that is beingperformed by the scientific crime detection labo-ratory of the Federal Bureau of Investigation inWashington, D. C. To meet the increase andinflux of investigations arising from sabotage andespionage activities, the laboratory has availablenumerous pieces of equipment and precisioninstruments that will aid in the advancement ofthis purpose. The laboratory of the FederalBureau of Investigation, being a service organiza-tion, offering assistance willingly in all mattersinvolving scientific crime detection, presentsitself to the cause of doing all in its power to

* Presented at Symposium of Optics in the National De-fenise at the twenity-sixth annual meeting of the OpticalSociety of America held in New York City, October 24-25,1941.

analyze and solve, limit and prevent any criminalactivities which are injurious to this country'sinternal security.

The laboratory staff is made up of many men,each one a specialist in a particular branch ofscience. The forensic applications of petrography,metallurgy, chemistry, serology, toxicology, spec-trography, physics, firearms identification, anddocument identification are numerous, and theyform the basis of the work of the laboratoryspecialists in the respective fields. Needless tosay, optical equipment is not found lacking.Optical instruments are probably used morefrequently than any other type of instrument.Optical instruments, because of their ability toreveal characteristics minute in size and manytimes significant in nature from the standpointof criminal work, and to expose other charac-

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teristics which cannot be observed with thehuman eye and which cannot be detected byequipment of another nature, are a necessity ina scientific crime detection laboratory. As anexample, the Federal Bureau of Investigationcrime detection laboratory in recent years hasbeen equipped with some of the most moderndevelopments in the optical field, such as thespectrograph, the densitometer, and high poweredmagnifying equipment.

The petrographer, for example, using thepetrographic microscope, which is equipped witha universal stage for mounting and observingthe specimen and which is provided with anauxiliary source of polarized light, determines theoptical characteristics of soils, minerals, dirt andd6bris. The refractive properties, the axialproperties of crystals, the polarizing properties,the crystalline form, if any, and the cleavage ofthe substance being examined-all of these char-acteristics can be determined optically. Conse-quently, in scientific criminal examinations ofthis type, in which comparisons of samples aredesired, a great significance is attributed to theoptical characteristics which are observed by thepetrographer. Many times, accurate measure-ments relative to the indices of refraction ofparticles of soil, crystals, minerals, or glass areextremely pertinent. To assure high accuracy inthis type of analysis, a double variation methodof determining the index of refraction is em-ployed. The double variation method makes useof two methods of varying the index of a liquid,namely by changing the temperature of the oiland by changing the wave-length of the lightused as an illuminating source. Therefore, if acrystal or a particular piece of glass, submittedas evidence, is to be examined in order to com-pare it with other specimens or simply to de-termine its index of refraction for identificationpurposes, the double variation method is appliedand accurate determinations of the indices of thecrystal or of the glass can be made.

In many petrographic cases, specimens of oilsand grease are submitted for examination inorder to determine if there are any foreignmaterials or abrasives present. The oil cup withthe oil contained therein or the catch-pan froma disrupted piece of machinery might be sub-mitted for investigation. The foreign materials

present are first separated from the oil bycentrifuging, and then the residue is analyzed todetermine the abrasive nature of the material.The abrasives recovered may be compared withknown abrasives maintained for comparison pur-poses in the laboratory or with abrasives ob-tained from particular sources in the plant or inthe immediate neighborhood of the disruptedmachine. Bv this method oftentimes it is possibleto localize the source of the contamination andthe destruction. Consequently, the petrographerfinds innumerable applications of optics in hisparticular field.

Metallurgy also figures significantly in theanalysis of cases involving sabotage and sus-pected sabotage. Evidence which is concernedwith the disruption of machinery by fracturingvitally important equipment or machine parts,with the dismembering of wire cables, etc., tocause failure and fracture of the cable when astrain is placed upon it, with the effect producedby the existence of metallic fragments of aforeign nature in lubricating systems, bearingsand other moving parts of machinery-examina-tions of this type receive the scientific considera-tion of the metallurgist. To analyze metallurgi-cally a particular specimen and to compare itwith other specimens which may lead to theuncovering of the saboteur or saboteurs, crosssections and longitudinal sections of the speci-mens are mounted so that their crystallinestructures may be observed. The sectionalmountings when observed with the metallurgicalmicroscope, employing vertical illumination,usually will reveal the similarity or dissimilaritybetween the specimens that are being compared.Also the nature of the industrial treatmentswhich were initially employed in the manufactureof the specimen as well as the functions, prin-cipally the stresses and strains, that the specimenwas made to perform as a component part of amachine, may be evident to the metallurgistafter an examination of the characteristics of thesectional mountings.

A case arises in my mind which depicts therepresentative type of work that this section isdoing in national defense. A tractor which wasmanufactured in a plant in the Midwest wasexported to Melbourne, Australia. When it wasreceived in that city a large deposit of fine iron

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granules was found in the oil pan. It was statedthat the tractor's timing gear, crankshaft, andbearings had been ruined by the granules, andit was believed that an act of sabotage hadbeen committed. A quantity of similar irongranules was discovered around the oil levelgauge sleeve of the tractor, adhering underpaint which had hardened. Inasmuch as thepaint was applied in the United States, thesegranules must have been present prior to theexportation of the tractor. The tractor in ques-tion was valued at 5000 and was of the typewhich some foreign governments, principallyGreat Britain and Australia, have converted intoarmored tanks for military purposes. A metal-lurgical examination was made, and the sampleswere revealed to be white cast iron. The polishedsections of the above specimens revealed themto be composed of cementite and pearlite withno graphite plates such as occur in gray cast iron.White cast iron is extremely hard and brittle.Because of this hardness, it was suggested thatit may possibly be used as an abrasive. Furtherinvestigations were carried out in this countryfollowing on leads revealed by the laboratoryexamination.

The metallurgical section of the laboratoryoften works in conjunction with another section,namely, the spectrographic section. This sectionis equipped with several microscopes with auxili-ary oculars and objectives to control the desiredmagnification of the specimens, a medium quartzspectrograph, an absorption spectrograph, a com-parator micrometer, and a comparator-densitom-eter. In the last decade, it has become evidentin the laboratory that many advantages mightarise, with regard to crime and its scientificdetection, if informative and accurate analysesof paint samples, usually minute in size, could beperformed. These examinations are carried outalmost exclusively by the spectrographic sectionof the laboratory, and they constitute probablyone of the most numerous examinations con-ducted spectrographically. However, it should bepointed out that many other types of metallicspecimens are examined by this section parallelto and in conjunction with a metallurgical exami-nation or a tool marks' examination. A toolmarks' examination is an examination in whichan attempt is made to affirm or deny that a

particular tool mark, for example, a jimmy markon a window frame, was produced by a particulartool or in the example referred to, a particularjimmy. A spectrographic examination of anymaterial adhering to the tool is made to deter-mine if it is or is not similar to the material orpainted object which was marked. Or thenagain, burrs or loose metallic particles from thetool may be deposited on the marked object,and in this case the deposited metal and themetal of the tool are compared spectrographically.

The primary advantages of the spectrographicmethod over other non-optical methods are:first, that only a very small sample of the evi-dence is used, the remainder being available forcourt presentation; second, that the examinationcan be carried out with great speed and accuracy;third, that the instrument is so sensitive thatelements and impurities present in extremelysmall quantities are readily detectable; fourth,that a complete record of the material burned isregistered on the photographic plate and alsothat this photograph is admissible as evidence ina court of law.

The spectrograph was employed a short timeago in the analysis of some 176 hacksaw bladessubmitted as evidence involved in damage to aNavy experimental aeroplane in the CurtissAeroplane Division, New York. Submitted alongwith these blades was one forty-five degree,one-inch hose ell aluminum alloy fitting whichwas used in the direct feeding unit from theship's gasoline tanks to the carburetor. Duringthe assembling of the flight motor of this plane,it was discovered that this fitting had beentampered with. A hacksaw blade had apparentlybeen used to cut the seventh thread of thefitting for the purpose of weakening its tensilestrength and to cause serious damage to the shipeither before or after it was placed into flight.There were also forwarded to the laboratorynumerous hacksaw blades which were securedfrom the employees in the experimental sectionof the plant. A spectrographic examination ofthe teeth of these blades limited the search forthe destructive blade from 176 to 17 blades.Seventeen of the blades spectrographically wereshown to have elements on them which weresimilar to the elements in the aluminum alloyfitting which had been tampered with. This

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limitation of hacksaw blades and suspects sig-nificantly simplified the criminal investigation.

Another interesting case that was handledspectrographically was the case of the wreck ofa streamliner passenger train. This train wasproceeding westward and the point of derailmentwas just east of a steel girder bridge over ariver. The members of the train and field crewsadvised that they saw nothing unusual along thetracks in that vicinity. Following the wreck, itwas observed that one of the rails had been bentin, and spiked in that position. This bent railwas then painted to disguise the bent sectionwhen the train approached the break in the rail.Because it was night and the light on the frontof the train was on, the reflection from thebright steel rails would ordinarily have indicatedto the engineer that the track was displacedfrom its proper path. The reflection from thatsection of the rail was removed by painting therail, and indications of the displaced rail werenot apparent. A claw bar, spike maul, trackwrench, jack handle, a small roll of wire, andtwo zipper jackets were found in the bottom ofa five-foot water hole, approximately 900 feetfrom the bridge. In the opinion of experiencedrailroad men this act was committed by menexperienced in this type of work. Their opinionwas based on the location selected for the derail-ment, on the fact that the derailer was arrangedon the outside of the curve, and on the fact thatthe rail displacement was effected in such amanner so as not to interfere with the operationof an automatic block signal in that vicinity.Subsequently, a cap from a paint can was foundat the scene, and this was also submitted to thelaboratory. Spectrographically it was possible tostate that the paint removed from the track, thesmears of paint on the zipper jackets, and thepaint on the paint can cover were all similar incomposition. A comparison was made with someknown paint samples submitted by the Con-Ferro Paint and Varnish Company, St. Louis,Missouri, and this paint was revealed as beingsimilar in color and composition to the paintpreviously submitted. However, the company'srecord did not indicate that this can of painthad been sold in the locality of the wreck. Allefforts to trace the buyer of such a can of painthave failed, and photographs of the two zipper

jackets were printed and exhibited in post officesthroughout the country with the request thatany person knowing the owner or owners of thejackets furnish that information to interestedauthorities. The interesting point about the caseis the success encountered with the spectrographin the analysis of paint specimens even thoughthe sample is extremely small, as was the sampleremoved from the two jackets. It is also pointedout that if at any time paint specimens possessdefinite layer structures, photomicrographs andphotographic comparisons of the sequence ofcolors are made on color film.

Since destruction to person and property canbe committed in innumerable ways, one canappreciate that many cases arise which requirethe specific attention of an expert in chemistry,toxicology or serology. Although cases which areconsidered by the toxicological and serologicalsections of the laboratory are not usually con-cerned with national defense, it is pointed out asa matter of interest only, that these sectionsutilize the optical equipment in the laboratorywhenever the specific occasion demands it. Theserological section has occasion to use its micro-spectrophotometer routinely in the identificationof blood by the observation of the absorptionbands of oxyhemoglobin.

The chemist, or more specifically the micro-chemist, finds the binocular microscope a neces-sity in investigations dealing with sabotage andespionage. The microchemist, when working withsmall bits of evidence, many times must observethe chemical and calorimetric tests being per-formed under the microscope. Furthermore, theapplication of colorimetry is in itself an extensiveand important application of optics in forensicchemistry.

Probably one of the most interesting types ofchemical cases, which have risen in importancewith the increase of sabotage and espionageactivities in this country, is the case involvingdestruction caused by spilling or placing acids orother destructive chemicals in or on equipmentbeing produced under the defense program. Todetermine the chemical employed and to observethe nature of the surface destruction as well asto make sample tests with suspected chemicalswhile in the process of their destruction, requires

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unlimited effort and acute and persistent obser-vation under the microscope. Much success hasbeen encountered along these lines, and it isevident that this success is due in great part tothe optical equipment which facilitates the workof the specialist.

Much more directly concerned with the generaltopic of this paper are the work and investiga-tions which are carried on in the firearms sectionof the laboratory. National defense work is animportant phase of the work of these specialists,and consequently it receives expeditious atten-tion, utilizing at all time equipment which isavailable and necessary. Several comparisonmicroscopes are at hand for visual work or formaking photographs for record purposes. Alsoseveral wide-field binocular microscopes, whichare extremely useful for the examination ofbullets, powders, cartridge cases, and the like,are available. The most recent addition to theequipment of the firearms section is a tool-maker's microscope for the accurate measure-ment of striations, depressions, and scratches onbullets and cartridge cases as well as for theapplications that it will have in tool marks'examinations.

The document section and a subdivision of itwhich has developed enormously since the de-fense emergency, namely, the cryptographic sec-tion of the Federal Bureau of Investigationlaboratory, is engrossed with the task of com-paring and analyzing documents, checks, codes,and ciphers. This particular group finds incessantapplications of the simple magnifier and micro-scope and also the opacimeter for paper com-parisons. The search for fluorescent invisiblewriting using ultraviolet light and the use ofultraviolet and infra-red photography for therestoration of secret and obliterated writing, areparts of their extensive field.

By this time the absence of references to

particular cases and examples may be becomingquite obvious; but it must be realized thatbecause of the nature of the crimes being con-sidered, it is not advisable to be specific lest themethod and manner of scientific crime detectionbe generally revealed and its effectiveness stunted.It is hoped that this paper has served to illustratein some small measure the type of work that isbeing done by the technical laboratory of theFederal Bureau of Investigation, especially withregard to optics, not overlooking, however, manyother fields of endeavor which are utilizedtherein. It may be of interest to you to know thatduring the month of September, 1941, 1548 morescientific examinations were performed than inthe same period of the previous year. Thisfigure indicates an increase of 282 percent in thenumber of examinations made.

It was in 1932 that Mr. Hoover, as part of hislong-range program for developing the efficacyof the FBI, initiated the crime detection labora-tory. At that time there was considerable skep-ticism among some police officials as to thepractical value of applying laboratory methods tocriminal investigations. Mr. Hoover's foresightin this respect has since been well proved. In1937, determined to afford police investigatorsof the nation the best staffed and best equippedlaboratory possible, the Director sent Mr. Coffey,who is presently in charge of the laboratory, toEurope where he studied the various scientificpolice facilities of foreign nations. He reportedback that American equipment and scientificpersonnel were equal to or superior to those inthe great criminological centers of Europe.

Today the FBI's laboratory staff numberssixty-five scientists, and its equipment is thebest in the world for the purposes used. Over2000 analyses are made each month, and itstechnical services are available without cost tothe police of the nation.

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