Lab director Carlisle Winslow believed that Davis and Cuno, military men who had served their country with distinction, could serve once again—and keep their communications about it to a minimum.
And secrecy was paramount. Koehler, who in his letters to his brothers discussed everything from the boils he’d been fighting to his political views, never mentioned his efforts on this case. “My work in the East is in a state of ‘unfinished business,’” he wrote them on April 21, 1933. “Some day maybe I will tell you all about it.”
He did tell Davis everything about his investigation. Koehler double-checked his measurements, his observations, and eventually his conclusions with his colleague.
Davis knew that in a typical mill planer machine, a rough board would be gripped between two steel cylinders before the feed rolls, which push and revolve the board forward at a constant speed. Past the rolls are sets of knives, positioned above and below the board. These are called cutter heads. The knives are fixed at equal spacing around cylindrical drums that Koehler would describe as looking like a “paddle wheel.”
The cutter heads would be positioned at the distance wanted for the thickness of the lumber, with the knives extending crosswise to the width of the board. They would then revolve at a high velocity and “dress,” or cut, the board’s upper and lower faces. Past the face cutters are the upright cutters. The number of blades in the upright cutters varies, and while they also revolve quickly, they’re not necessarily spinning at the same speed as the face cutters. They dress the edges of the board as it is fed through the planer.
The process wraps up when two outgoing feed rolls, which are timed exactly with the first pair, make sure the board gets out of the planer. If none of the settings are manually changed, board after board should have the same markings from the planer, cut after cut.
Two months of dead ends on the East Coast led Koehler back to Madison and a private workspace to continue studying the ladder. “I concluded,” he said, “that it had not divulged all its clues.” (Courtesy: Dr. Regis Miller/Forest Products Laboratory)
Koehler had deduced in New Jersey that Rails 12 and 13 had come from one board cut in two, giving a “twofold record of the planer cycle, which was of great value in checking observations.” Davis confirmed there was no conspicuous evidence of “nicks or dull spots” in the planer knives and that the faint intermittent grooves on one edge of each upright were sharp cuts, not so-called “chip marks,” which can happen if a chip sticks to a knife edge.
He recalibrated Koehler’s measurements and backed up that there was one revolution every 0.86 of an inch on one edge of Rails 12 and 13. Further, they found there were six “short, shallow, equally-spaced waves” impressed on the surface in that distance. That meant there were six knives dressing the edges of the lumber.
Turning to the faces, they calculated that a periodic but slight irregularity happened in the planing every 0.93 inch on the top and bottom of the wood. The two scientists noted there were eight knife cuts every 0.93 inch per revolution, indicating there were eight knives dressing the faces of the lumber.
Koehler called these results “a kind of time-clock record.” Davis knew that upper and lower face cutters of planers in eastern pine mills were usually driven at roughly 3,000 revolutions per minute, or 50 per second. The wood traveled an inch every one-fiftieth of a second.
Doing the math using the calculations he and Davis had come up with, Koehler determined that meant Rails 12 and 13 were fed through a planer at around 230 feet per minute. That was fast by eastern mill standards, more than twice as fast, in fact, as the typical pace. The cutters dressing the edges went even faster than those cutting the faces, since they made a complete revolution while the feed was going a shorter distance.
What this all meant was that the machine that cut the ladder’s bottom uprights had six knives cutting its edges and eight knives cutting its faces, that the edge cutters went faster than the face cutters, and that the machine that did it was really fast.
They still didn’t know though exactly how it all had happened. But wood wasn’t supposed to look like this, and likely the person who had dressed it had eventually spotted the abnormalities himself. Koehler and Davis were banking on that possibility.
By now, Koehler had heard back from the three major companies who manufactured planers that fit the general descriptions laid out. He met personally with representatives from Yates-American in the company’s Beloit, Wisconsin, headquarters after he returned from New Jersey. There he received a list of 420 firms the company had sold similar machines to, from New Jersey to Alabama. The planers in question were the A-4 and A-5 versions, as well as the company’s models number 94 and 95. S. A. Woods Machine Company in Boston sent a list of thirty-six firms that had purchased its #404B planer model. Fay & Egan out of Cincinnati responded that it had not sold any of those machines.
From April 10 to 13, 1933, Koehler wrote a form letter to all of the firms on Schwarzkopf’s New Jersey State Police Department stationery and with the colonel’s signature.
“An effort is being made to trace some North Carolina pine used in connection with a crime,” the letter began. “We are trying to trace it to the mill that dressed it and from the mill to the consumer. Fortunately there are several identification marks on the lumber which may make it possible to do so, and your cooperation is solicited.”
After laying out the details of the planer in question (eight knives in top and bottom cutter heads, six in the side heads, and so on), the letter asked the companies if they had dressed 1x4-inch North Carolina pine on it “within the last 3 or 4 years.” Koehler added that the wood in question was not finished, but “a common or box grade.”
If they had such a machine, he said he would write with more particulars to determine if “it was dressed at your mill.”
Then, as if to assuage any fears, he wrote, “You may be assured that giving this information will not involve you in any way, but that in so doing you may be rendering the public valuable service. May we request that you keep this matter confidential, since publicity might frustrate our plans.”
The initial response was not good.
The Scarboro-Safrit Lumber Company in Mount Gilead, North Carolina, wrote back to say, “We beg to advise that we do not have a planer or matcher carrying 8 knives in the top and bottom cutter heads. We have never dressed any of our lumber on this kind of a planer.”
The Fairfax Manufacturing Company in Orangeburg, South Carolina, had a planer with six knives each on its top and bottom cylinders, as did the A. C. Tuxbury Lumber Company, which wrote, “This eliminates us as a possible source of supply for the lumber mentioned in your letter.” The Douglas Machine Company in Luverne, Alabama, had twelve knives on top and bottom of its planer.
The Shippen Hardwood Lumber Company was “unable to give you any light or data to the machine work etc. that you are seeking.” The Whittle and Slade Lumber Company in Eufaula, Alabama, wrote that its planer “does not answer” to the description given.
The Dickson-Henderson Lumber Company in Ocilla, Georgia, couldn’t help because it was out of business. The Traylor Engineering and Manufacturing Company in Allentown, Pennsylvania, couldn’t help because it didn’t use 1x4-inch pine in its plant.
As April progressed, the investigation did not, even as Koehler spent all of his “spare time” tracking down leads. A number of letters were returned marked “Unclaimed,” “Unknown,” and “No such post office in State named.” Those who did respond weren’t any more helpful.
Victor W. Stewart with the Colonial Pine Company in Petersburg, Virginia, did “not believe that we will be able to be of any real assistance to you in this matter.”
The Woodward Lumber Company in Augusta, Georgia, insisted it was “regretting our inability to help you in this matter.” The Jeffreys-McElrath Manufacturing Company was “very sorry.” The E. S. Adkins & Company representative in
Maryland told of the “slight difference in pine that grows in this section and that grown further south.”
Others recognized what case they were being asked to help with, even if they couldn’t. The J. E. Paterson Lumber Company in Mobile, Alabama, wanted to “assure you that it will be treated confidentially.” The Wisconsin Alabama Lumber Company wrote, “We are sorry we are unable to assist you in tracing this lumber as we would like nothing better than to help apprehend the perpetrators of this terrible crime.”
Maybe summing up what others were thinking, if not saying, was the representative who responded from the Kentucky Lumber Company in Columbia, Mississippi. “We wish that we could be of some service to you,” he wrote, “but this is impossible.”
At the same time he was pursuing the North Carolina pine connection, Koehler was actively trying to trace the planing of the Douglas fir rails, Numbers 14, 15, and 17. Bornmann had believed them to provide “no possibilities” because they didn’t have distinguishing characteristics, but Koehler and Davis, upon taking a closer look in the lab, found one in particular. Every eighth planer mark was more pronounced, indicating there were eight knives in the upper and lower cutting heads, one of which was “not lined up perfectly with the others.”
Plus, one of the fir rails had a patch of red paint on one edge and one face that was about half the size of a hand. It had been identified by the federal Bureau of Chemistry and Soils as red iron oxide roof paint, but Koehler had learned it was also used in cargo shipments to mark off different lots.
Koehler knew Douglas fir came from the Rocky Mountains and forests west to California, so he reached out to the head of the West Coast Lumbermen’s Association, run by Lieutenant Colonel W. B. Greeley, who had also served in the 20th Engineers during World War I. Koehler hoped to get a list of mills that shipped Douglas fir out to the Atlantic Coast.
Greeley’s associate, C. J. Hogue, who was in charge of trade extension and technical service for the association, responded to Koehler that there was “very little possibility” that lumber would have been shipped from the interior of the country to the East by rail, because the freight charge would have been too high for such a low-grade wood. Therefore, they concluded it likely had been shipped by boat.
In an April 19 note to Captain Lamb, Koehler deduced, then, that it “practically eliminates the possibility of its having come from Pittsburgh, Buffalo, Chicago or any number of inland towns which would make it impossible to trace it.”
Working on both the pine and the fir, Koehler believed that “it should be possible to narrow down the origin of the lumber a great deal more than with only one kind of lumber to work on.”
He was also working on the birch dowels, believing them now to be yellow birch, since it weighs significantly more than white birch. He sent back Number 18 to Lamb by registered mail after the paint expert at FPL also checked it out and concluded that the surface coating on the dowels came from handling, not manufacturing.
That said, Koehler and Davis had reason to hope. Fourteen firms out of the 456 queried replied that they had planers that fit the general specifications, including the Woodville Lumber Company in Crawford, Georgia, which indicated it had an A-5 Yates-American model and was willing “in any way to help you check up on this question.”
The Waccamaw Lumber Corporation in Bolton, North Carolina, responded that it had two high-speed planers that were the models in question, but it doubted how much it could help, as its planing mill foreman had recently died.
Others like Keystone Lumber in Pittsburgh; Halsey Lumber Mills in Charleston, South Carolina; Roper Brothers Lumber in Petersburg, Virginia; Millen Lumber in Millen, Georgia; and American Car and Foundry in New York continued the conversation, as they, too, had at least one of the planer models in question.
A follow-up letter, also written by Koehler but sent out by Schwarzkopf, went to all of the companies who had answered in the affirmative. If Schwarzkopf’s name and location had not tipped them off about what crime he was writing about, the next letter was even more blunt.
“The following request is made of you in the strictest confidence, being in connection with the Lindbergh kidnapping and concerns lumber which we are trying to trace and which is a part of the ladder used in this kidnaping and your cooperation is solicited,” it stated before explaining in an enclosed two-page, detailed description Koehler had prepared on Rails 12 and 13 and an exaggerated sketch of the planer marks on the edges of the North Carolina pine. The letter continued,
The three most logical theories so far developed as to the cause of the shallow interrupted grooves are: 1) A groove cutting knife was inserted in one of the side cutter heads merely for balance but was not set back far enough to completely clear the wood, therefore, it cut a shallow groove each time it came around; 2) a groove cutting knife was ground down to a straight edge, except for a small projection which remained on the edge and cut the shallow groove each time it came around; 3) the edge of one knife was badly damaged except for a portion 0.2" wide which was the only part of that knife which did any cutting.
But then, as if owning up to the long odds investigators faced, the letter read, “We suggest, however, that you consult with your planing mill foreman and develop your own theory as to the probable cause of the shallow interrupted grooves. . . . It is the general opinion that whatever caused the shallow interrupted grooves was something unusual and would be remembered by the planing mill foreman.”
It was not as if there weren’t doubts about Koehler’s and Davis’s conclusions to date. The engineers at Yates-American looked over one of the rails and concluded that both sides of the board were planed with six-knife heads, not an eight-knife head and a six-knife head as the FPL scientists had reported. This led Koehler to second-guess himself in a note to Captain Lamb, saying that “perhaps we have put too much emphasis on the ‘peculiar markings’ on the edge of the rails 12 and 13.”
He’d further second-guess himself when H. A. Perkins, the president of the Production Machinery Sales Corporation in New York City, was brought to Trenton for his own analysis of the ladder, paying particularly close attention to Rails 12 and 13. In his forty-five years of experience, including twenty-five as the founder of the American Woodworking Machine Company, he had become known “as an authority on woodworking machinery.” Perkins, who refused to be compensated for his efforts aside from his train fare to and from New York, believed that the edges of the rails in question had been planed with a six-knife head on one side and a four-knife head on the other.
Responding to Perkins’s analysis to Lamb, Koehler said, “Anyone who wishes to make a different interpretation than I made of the planer marks should be encouraged to do so, especially if he thinks that with a different interpretation his machine set-up would fit the case. We can later straighten out any differences of opinion.”
Koehler continued to soldier on despite the doubts. Letters to lumber mills were all fine and well, but he knew he needed wood to analyze. He encouraged Schwarzkopf to send out yet another letter to the now thirteen companies with the planer models in question, asking for two pieces of wood, preferably from two separate strips, of 1x4-inch North Carolina pine, two to three feet long, dressed on the machine in question.
Koehler wanted the lumber to be as clean as possible, but at the same time he wanted samples from at least two years earlier, nothing recently dressed, as the crime had been committed in March 1932. He was presuming that the ratio of the speed of the side heads to the horizontal speeds, and likely to the feed as well, hadn’t been changed in that time.
In the June 23, 1933, correspondence, the head of the New Jersey State Police encouraged the companies to send the samples directly to “Mr. Arthur G. Koehler, US Forest Products Laboratory, Madison, Wisconsin,” for a “critical check-up of the stock used in the ladder in question.”
Koehler received dozens of wood samples every month at the Forest Products Laborato
ry, and by including the fake middle initial that had appeared on his high school graduation program, samples related to the Lindbergh case could go straight to the top of the pile. At the same time, a package addressed to “Arthur G. Koehler” would not draw any extra attention from his colleagues.
Schwarzkopf concluded, “No letter of transmittal need accompany any samples sent to Mr. Koehler, as the assumed middle initial in his name will indicate the purpose of the material.” Twelve of the companies agreed to send in samples.
This is where John Cuno’s knowledge of sawmills and logging activity in North Carolina came in. There was a chance that many of the mills in that region had second-hand planers and thus would not be on the original list from Yates-American or S. A. Woods.
So Koehler and Cuno consulted the Lumberman’s Directory, which held a list of all the sawmills in the country, and found those listed that were planing North Carolina pine or shortleaf pine from New Jersey to eastern Alabama. After they crossed off those firms they had already written to, the list included 1,140 companies.
Koehler asked Lamb if he could correspond with them directly instead of using Schwarzkopf’s letterhead and signature. The captain, though not quite clear about what his wood expert was doing, still agreed.
Koehler used much of the same phraseology as in the other form letters except with no mention of Lindbergh, saying only that FPL was “assisting the police department of an eastern state in tracing the origin of some lumber used in connection with a major crime.” His letter ended with the familiar request that the recipient “keep this matter confidential as far as possible, since publicity might frustrate our plans.”
In response, eleven more mills reported having planers that fit those characteristics and saw fit to render a “valuable public service” by shipping their wood to Madison, Wisconsin.
The E. H. Barnes Company in Norfolk, Virginia, sent its two pieces of 1x4-inch wood by parcel post. So, too, did the J. H. Steedman Lumber Company in Clayton, Alabama, along with a note from the owner saying that his company was “only too glad to be of any help to you of any nature in this matter. If the above does not cover the subject and is not full enough kindly advise and we will be glad to go into the matter of shipments more fully or as full as we can.”
The Sixteenth Rail Page 11