The tall cranes, which often carry booms (known to the trade as “sticks”) of 120 feet or more, are assembled on the ground, at the construction site. If you’ll notice, most of the tall booms are built as steel lattice-work structures, and are thus comparatively lightweight. Usually, the machine arrives on the scene on its own, carrying only the base stub of the boom.
The sections for the full length of the boom usually arrive separately, via trailer-truck. At site, the stub of the boom is lowered to a horizontal position, and the sections of the finished boom laid out on the ground, attached together (much like a child’s erector set), then mounted on the stub, and raised into position by cables attached to the crane body.
Likewise, extensions can be added when needed by laying the boom on the ground.
The use of these conventional rigs has been steadily declining, however, in favor of the “tower crane.” These are the cranes that sit in the middle of a site and can be raised after they have been erected. The center column on which the control cab and the moving “head” sit is built up to three or four stories. As the building rises around the crane, added height is built onto the center column, and the whole top assembly is “jumped” upward.
Halmos reports that tower cranes have largely eliminated the need for elevators (known as “skips”) and the lifting of loads from the ground by mobile cranes. “The tower crane operator can see not only what he’s picking up, but can spot the load almost anywhere on the job, without a lot of elaborate signaling.”
Submitted by Laura Laesecke of San Francisco, California. Thanks also to Paula Chaffee of Utica, Michigan; Lawrence Walters of Gurnee, Illinois; James Gleason of Collegeville, Pennsylvania; and Robert Williams of Brooklyn, New York.
What is “single-needle” stitching, and why do we have to pay more for shirts that feature it?
You’d think that at fifty dollars or more a pop, shirtmakers could afford another needle or two. Actually, they can.
“Regular” shirts are sewn with one needle working on one side of a seam and another needle sewing the other side. According to clothing expert G. Bruce Boyer, this method is cheaper and faster but not as effective because “Seams sewn with two needles simultaneously tend to pucker. Single-needle stitching produces flatter seams.”
Submitted by Donald Marti, Jr., of New York, New York.
Why do dogs wiggle their rear legs when scratched on their belly or chest?
Maybe there is a Labrador retriever out there writing a book of canine Imponderables, trying to answer the mystery: Why do humans kick their legs up when you tap the area below their kneecaps? The leg wiggling of dogs is called the scratch reflex, the doggy equivalent of our involuntary knee-jerk reflex (or, as it is known to doctors, patellar reflex).
Anatomist Robert E. Habel, of Cornell University’s College of Veterinary Medicine, wrote Imponderables that the scratch reflex allows veterinarians to diagnose neurological problems in dogs:
Because the same spinal nerves pass all the way down to the midline of the chest and abdomen, you can stimulate the scratch reflex anywhere from the saddle region to the ventral midline. You can test the sensory function of many spinal nerves and the motor function of the nerves to the hind limb (they don’t wiggle their forelimbs). If the dog moves the hind limb, it means the spinal cord is not severed between the origin of the nerve stimulated and the origins of the lumbar through first sacral nerves, but the cord may be injured above the level stimulated.
A dog is not necessarily injured if it doesn’t exhibit the scratch reflex. In fact, Dr. Habel reports that his hound doesn’t respond at all.
What function does the scratch reflex serve? Nobody knows for sure, but that doesn’t stop dog experts from theorizing. Breeder and lecturer Fred Lanting believes that the wiggling might be a “feeble or partial attempt” to reach the area where you are scratching. Just as scratching ourselves sometimes causes the itch to migrate to other parts of the body, Lanting believes that scratching a dog may cause itchiness in other regions.
Dog expert and biology instructor Jeanette Hayhurst advances an even more fascinating theory, which is that the scratch reflex might help dogs survive. The movement of the back legs during the scratch reflex resembles the frantic movements of a puppy learning to swim. The scratch reflex might be an instinctive reaction to pressure on the abdomen, the method nature provides for a puppy to survive when thrown into the water. Newborn pups also need to pump their back legs in order to crawl to reach their mother’s teat.
We’d like to think that our human knee-jerk reflex might also have a practical purpose, but we’ll leave it to the dogs to solve this particular mystery.
Submitted by Shane Ellis of Mammoth Lakes, California. Thanks also to Kurt Pershnick of Palatka, Florida; Sonya Landholm of Boone, North Carolina; Alina Carmichael and Pat Kirkland of Lake St. Louis, Missouri; Sherry-Lynn Jamieson of Surrey, British Columbia; Sofi Nelson of Menomonie, Wisconsin; and Scott Wolber of Delmont, Pennsylvania.
Why do so many sundials have Robert Browning’s lines “Grow old along with me! The best is yet to be” inscribed on them?
Although not every sundial has a motto on it, most do; the tradition dates from antiquity. None of the many sundial makers and books about sundials we consulted could explain the reason for putting the motto on the sundial in the first place. Timothy Lynch, president of the sundial maker Kenneth Lynch & Sons, speculates that it was originally put there “for the personal gratification of either the maker or the receiver.”
The sundial makers we spoke to have standard mottoes or will custom-inscribe a customer’s personalized motto. They unanimously agreed with Lee Brown, a designer at Whitehall Products, who told Imponderables that virtually all mottoes refer to the passage of time.
Why are Browning’s lines the most popular? (Their only competitor in popularity is Tempus Fugit—“time flies”—a pithier if less poetic motto.) Ben Brewster, president of Colonial Brass, the largest manufacturer of sundials in the United States, has a simple theory with which the other sources agreed: Most quotations about time are depressing, or at least downbeat. A look at some of the suggested inscriptions used by Colonial Brass will give you the idea:
“Time takes all but memories.”
“Time waits for no man.”
“You ask the hour, meanwhile you see it fly.”
“Watch for ye know not the hour.”
“Time passeth and speaketh not.”
Not the kind of words to send your losing football team bursting out of the locker room in renewed spirits, are they? But Browning’s words are reassuring, making old age seem secure and downright romantic.
In her book Sun-Dials and Roses of Yesterday, Alice Morse writes:
One almost unvarying characteristic of the sun-dial motto might be noted—its solemnity. A few are jocose, a few are cheerful, nearly all are solemn, many are sad, even gloomy. They teach no light lesson of life, but a regard of the passing of every day, every hour, as a serious thing.
Morse’s book was written in 1922, when most mottoes were biblical quotations. (Her favorite was this far-from-upbeat citation from Chronicles: “Our days on earth are as a shadow, and there is none abiding.”)
For better or worse, we live in a society that has a relentless need to find optimism in any situation. Perhaps our fondness for the Browning quote shows a deep-seated psychological need to evade not only death but some of the hardships of old age. After all, better to spout platitudes than to confront the pain in this actual motto sent to us by Brewster, who remarked that its message was a little less uplifting than Browning’s bromide:
What Cain did to Abel
Brutus to Caesar was quick.
What Kip B. and Esther’s sister
Edith did to Esther and me
Was Torture—slow and fatal
May God forgive them.
Submitted by Sheryl Aumack of Newport Beach, California.
For a whole collection of sundial mottoes, see The Book of Sun-Di
als by Mrs. Alfred Gatty.
Why do babies sleep so much? Why do they sleep so much more soundly than adults or older children?
This is Mother Nature’s way of preserving the sanity of parents.
And there’s an alternative, less cosmic, explanation. Dr. David Hopper, president of the American Academy of Somnology, told Imponderables that sleep is crucial to the brain development of infants. After birth, the average infant spends sixteen to eighteen hours asleep per day. Up to 60 percent of that time is spent in REM (rapid eye movement) sleep, more than twice the percentage of adults. What is the significance of their greater proportion of REM sleep? Dr. Hopper explains:
REM sleep is the stage of sleep that dreams are associated with. Brain wave activity is very active during this stage and closely resembles an awake state. It is sometimes called paradoxical sleep because the brain is very active as if awake but the individual is deeply asleep. By one year of age, the brains of babies are sufficiently developed to begin cycling of four distinct NREM (non-rapid eye movement) sleep stages with REM sleep.
Although sleep researchers still do not understand precisely how this works, REM sleep seems crucial to the development of the central nervous system of infants. The NREM “quiet sleep” is far from a waste of time, though, for the pituitary hormones, crucial for growth, are released during this phase of sleep.
Parents will be glad to inform anyone willing to listen that their babies don’t always sleep soundly, yet the cliché persists that anyone who can withstand interference from sound or light while snoozing is sleeping “like a baby.” The solution to this paradox lies in the unique sleep cycle of newborns. The reason why babies sleep like a log much of the time, as we learned above, is because they are in REM sleep 50 to 60 percent of the time. It can be difficult to rouse an infant during REM sleep; yet the same baby might awaken quite easily when in any stage of NREM sleep.
The proportion of REM to NREM sleep gradually decreases during the first year of life, and babies sleep for longer periods at a stretch. Still, they may be fussier and wake up more easily, especially if they are being weaned from breast milk, which studies show truly does help babies “sleep like a baby.”
Submitted by Father Gregory A. Battafarano of Niagara Falls, New York.
What causes the film that forms on the top of the chocolate pudding I cook? Does this film appear on any kind of pudding?
We went straight to the makers of Jell-O brand pudding. The General Foods Response Center replied:
When pudding has been heated and then allowed to cool while directly exposed to air, the starch on the surface releases water. This evaporation hardens the texture of the top and causes a film to form on any pudding that requires cooking. Incidentally, if plastic wrap is placed directly on the surface of the pudding, while cooling, it prevents the water vapor from escaping and the film from forming.
General food researcher Noel Anderson told Imponderables that pudding film is actually a “starch gel,” a combination of sugar and starch that forms a moisture barrier that will not break down unless subjected to intense heat.
Submitted by Linda Wiley of Berlin, New Jersey.
Why does milk obtain a skin when heated, while thicker liquids, like gravy, lose their skin when heated?
Proteins and starch react differently to heat. When heated, the protein in milk coagulates; the fat globules no longer can be suspended in water and, being lighter than water, float to the top. Bruce V. Snow, a dairy consultant, told us that the fat globules “adhere and form a surface skin when the liquid ceases to boil or simmer heavily.”
But when gravy is heated, the starch, which has formed the skin in the first place, breaks down. Since starch is more soluble than protein, the result is that the ex-skin is reabsorbed into the rest of the gravy. The same process can be seen when soup is reheated after a skin has “grown” in the refrigerator.
Submitted by Beth Oakley of Ishpeming, Michigan.
Why do the tags on the left side of the right back pocket of Levi’s jeans come in different colors? What is the code?
If you haven’t noticed the different colors on the tags on the back pockets of Levi’s jeans, you just haven’t been looking at enough rear ends lately, or else it’s time for that eye check-up you’ve been avoiding for the last five years or so. Actually, the folks at Levi Strauss & Co. call them “tabs,” not tags.
Lynn Downey, the company historian, says that tabs were originally created to make Levi’s stand out from the competition. Tabs were the brainchild of an in-house advertising manager in 1936, and have been on all Levi brand jeans ever since. The design of the tabs and their position on the jeans are registered trademarks of Levi Strauss & Co.
There are now four different colored tabs (red, orange, silver, and cream) and they do indeed signify something—the type of construction used to manufacture the jeans. Although the consumer may not be aware of it, Levi Strauss spokesperson Jill Novack told Imponderables that many stores place all of the red-tab Levi jeans together, the orange together, etc. Here, in descending order of sales, are the four different colored tabs and what they mean:
1. Red. Red-tab Levi’s feature the classic, detailed construction: five high-sloped pockets; six rivets in the front pocket; single-needle work on the top stitching; double stitching on the back pocket, which flares slightly. All 501s have red labels, but so do many other popular styles: 505, 506, 509, 517, 550, 583, 584, etc.
2. Orange. Orange-tabs often look superficially like their red-tab counterparts. In fact, some lines, such as the 505 and 550, have both red- and orange-tab versions. But orange-tab jeans have slightly less expensive finishing and tend to cost a few dollars less than red-tab Levi’s. Here’s why: Orange-tabs have five rather than six rivets in front; more gradually sloping pockets; double-needle rather than single-needle work on the top stitching; and their pockets are simpler, with the stitching on the back pockets parallel rather than flared. Most of the 500 series not named above have orange tabs.
3. Silver. Levi’s “fashion forward” contemporary jeans line features silver tabs. These jeans are identified by names rather than numbers, and are often available only on a seasonal basis. Baggy jeans, anti-fit, and sport jeans are all placed in the silver line. The silver line tends to contain the most expensive Levi jeans.
4. Cream or Natural. The rarest of the tabs is the so-called natural tab, with a cream color that is the untreated natural color of the tab fabric, with brown lettering. The natural tab can be found only on Levi’s “Naturals” line, jeans that are, appropriately enough, naturally colored. Levi Strauss spokesperson Brad Williams told us that Naturals are softer to the touch than all their other jeans because they are the only ones that contain no dye. For technical reasons, starch must be used when applying dyes to jeans. As the consumer continues to wash most jeans, the starch gradually is eliminated from the garment. This lessening of the starch content is the reason why jeans get more comfortable after repeated washings.
Or course, we knew nothing about this color coding before we started researching this Imponderable. So the next time we are in the market for 501’s, we will undoubtedly become paralyzed with self-consciousness. Do we buy the red-tabs and prove that we are fashion snobs of the worst order, demanding construction details that we never noticed in the first place? Or do we try orange-tabs, and advertise to the rest of the world how cheap we are?
Submitted by Cathy Pearce and Heather McCausland of Lakeland, Florida.
How did Levi’s 501 jeans get their number?
Levi Strauss (yes, there was a real Levi Strauss) was a dry goods merchant in California and sold a wide range of products. The original Levi jean was the 501, and this number was simply its arbitrary stock number, according to Levi Strauss & Co. spokesperson Brad Williams.
Strauss disliked applying the word “jeans” to his garment, so he promoted the 501 as “waist-high overalls.” Just think, if his company kept that name into the 1970s, chances are that high-fashion designers like
Gloria Vanderbilt and Calvin Klein wouldn’t have foisted “designer waist-high overalls” on a gullible public at triple the prices of Mr. Strauss.
Submitted by Sharon Michele Burke of Los Altos, California. Thanks also to John Hyatt of Boise, Idaho.
Why do the bricks used in constructing houses come with three holes in them?
We have the feeling that when Lionel Richie and the Commodores sang “Brick House,” this wasn’t what they had in mind. In fact, we didn’t even know there were holes in bricks until reader Sandra Sandoval brought this to our attention.
When we get a brick Imponderable, we know where to head—to the Brick Institute of America and its director of engineering and research, J. Gregg Borchelt. He informed us that these holes are known to brickophiles as “cores,” and that there can be zero to twelve cores in a “unit,” or individual brick. The main reason for the cores, according to Borchelt,
is to improve the drying and firing process of the unit. The clay dries more easily and reaches a more uniform firing temperature with the cores present. Tests were conducted to show that the presence of cores does not reduce the overall strength of the brick.
Are Lobsters Ambidextrous? Page 6
