Are Lobsters Ambidextrous? (22 page)

What function does the gravel serve?

 

1. According to William A. Good, executive vice-president of the National Roofing Contractors Association, the gravel helps to protect the roof membrane (“a combination of waterproofing and reinforcing materials” located just above the insulation and below the gravel) from puncture or tear by foot traffic from construction workers, dropped tools, hailstones, or stray meteorites.

2. Gravel provides a lighter, more reflective, color than black asphalt, making the roof more energy-efficient. A side benefit: Gravel lessens the ultraviolet degradation of the roof membrane that would exist if the membrane were exposed directly to the sun.

3. The gravel acts as ballast. In windy conditions, the membrane, which is, in essence, tar paper, can actually lift up and even fly off if left exposed.

4. The gravel provides more secure, less sticky, footing for anyone walking on the roof, increasing the safety not only of maintenance workers but of civilians. (Remember, frisbees and baseballs have a much better chance of landing on a flat roof than a pitched roof.)

5. The gravel acts as a fire retardant.

 

But gravel’s status as the ballast of choice is in jeopardy, according to Boon:

 

Today, newer technology has allowed for single-layer roofing systems. Larger, ¾″-1½″-diameter stone is used…to hold the roofing system in place. The larger stones provide the same protection from sun, traffic, and fire, and the larger size reduces the potential for wind blow-off.

 

Submitted by Howard Livingston of Arlington, Texas
.

 

There
are many miniature dogs. Why aren’t there any miniature house cats?

Our correspondent, Elizabeth Frenchman, quite rightly points out that there are legitimate breeds of dogs that resemble ro
dents more than canines. If poodles can be so easily downsized, why can’t Siamese or Oriental cats? If dogs can range in size between the pygmyesque Pekingese or a sausage-like Dachshund to a nearly three-foot-high Borzoi or a lineman-shaped Saint Bernard, why is the size variation so small in cats?

According to Enid Bergstrom, editor of
Dog World
, the answer is in the genes. Bergstrom says that dogs are the most genetically variable mammals, the easiest to breed for desired characteristics. The genes of cats, on the other hand, are much less plastic. If you try to mix two different breeds of cats, the tendency is for the offspring to look like an Oriental tabby. Of course, as dog breeder Fred Lanting points out, domestic breeds are miniature cats of sorts, the descendants of the big cats found in zoos.

Helen Cherry, of the Cat Fanciers Federation, told
Imponderables
that felines could be reduced somewhat in size by interbreeding small cats, but she, as well as all of the cat experts we spoke to, insisted that they had never heard of any interest expressed in trying to miniaturize cats. A representative of the American Cat Association remarked that a cat is small enough already.

Cat associations and federations are conservative by nature. Helen Cherry predicted that miniature cats would not be allowed to register or show or be “acknowledged in any way.” It isn’t easy being small.

 

Submitted by Elizabeth Frenchman of New York, New York
.

 

What
is the meaning of the numbers inside the arrows of the triangle on recyclable plastics? And what do the letters below the triangle mean?

Both the numbers and the letters signify the composition of the plastic used in bottles and other containers. Imagine the prob
lems at recycling centers if workers were forced to judge, by eye, whether a bottle was made out of polypropylene or polyethylene terephthalate, to mention merely two of the hardest to spell plastics.

So the Society of the Plastics Industry, Inc., developed a voluntary coding system for manufacturers to classify plastic containers according to their resin composition. The most common plastics received the lowest numbers. The letters are abbreviations of the dominant resin from which the container is made. If containers are made from more than one material, they are coded by the primary material:

The use of the plastic container coding system is voluntary, and the manufacturer does not in any way guarantee that the product will be recyclable or that the resins in the container will be compatible with other containers that have the same code number.

This disclaimer is necessary for several reasons. Virgin materials are manufactured for specific applications; not all polypropylene products, for example, can be blended successfully. In some cases, the intended application for the recycled product might be more demanding than its original use. And plastic, like any other material, can be contaminated by the contents of the container during its original use. We know we have a strong preference not to have the plastic containers recycled at some of the fast food joints where we have eaten.

 

Submitted by Dave Hanlon of Aurora, Illinois
.

 

Why
are there no public bathrooms in most supermarkets?

After trying about ten different supermarket chains, we got one on-the-record response—from giant Kroger. Off the record, we got the same response from other stores as we received from Kroger’s customer relations representative, Ginger Rawe: “Restrooms have always been available for customers’ and employees’ use, while not always visible to the public.”

What incentive do supermarkets have to make restrooms noticeable or to encourage their use? Shelf space is at a premium, and supermarkets already suffer from very low profit margins. And stores have no desire to encourage noncustomers off the street to use restrooms. Department stores have long made it a policy to locate their bathrooms in the most obscure nooks of their space. You may have to walk past some unopened cartons or some unpackaged meat, but you’ll find every supermarket has bathrooms. The next time nature calls, just ask a clerk—assuming you can find one. He or she will know how and where to find relief.

Incidentally, supermarket bathrooms are coming out of the closet, so to speak. With the advent of food superstores and warehouse supermarkets, many chains are trying to keep customers inside the store as long as possible, and floor space isn’t quite as tight as in “regular” supermarkets. Some chains are making their bathrooms user-friendly by posting signs so that customers can actually find them. Now if they would just stock the bathrooms with paper towels instead of those infernal hand driers, we’d be content.

 

Submitted by Michael Reuzenaar of Colorado Springs, Colorado. Thanks also to Jadon Welke of Hebron, Indiana
.

 

Why
do babies blink less often than adults?

Babies blink a lot less than adults—many babies blink only once or twice a minute. The purpose of blinking is to spread tears over the surface of the eyes. Adults vary widely in their blink frequency, and such exigencies and circumstances as corneal touching, irritation, drying, foreign matter entering the eye, and emotional distress or excitement can all cause the blinking rate to rise dramatically.

Ophthalmologists we contacted are full of theories but not a definitive answer. James P. McCulley, of the Association of University Professors of Ophthalmology, points out that the nerve structure of the infant’s eye is much less well developed than its adult counterpart. Babies don’t even manufacture tears during their first month of birth, so they clearly seem immune to the pain of dry eyes that would afflict adults who don’t blink more often.

Ophthalmologist Samuel Salamon, of the Cataract Eye Center of Cleveland, Ohio, muses over other possible explanations:

 

It is puzzling to us as to why babies’ eyes don’t simply dry out. Of course, they don’t spend that much time with their eyes open and the tiny bit of mucus that the eyes manufacture is usually enough to keep the front surface of the eye, the cornea, moistened sufficiently.

Babies probably do not need to blink as often as adults because their fissures are much smaller. That is, much less of their front eye surface is exposed to the environment both because of the shape of their skulls and because their eyelid openings are very small. Thus, the eyes dry out much more slowly, and need lubrication much less often.

 

Some ophthalmologists we contacted also speculated that babies’ blinking rates may not be caused as much by emotional
components as adults’ are. Perhaps, but any parent who has had a baby cry for hours for totally unexplained reasons may hesitate to believe that stress isn’t a major part of the infant’s ecosystem.

 

Submitted by Julie Ann Jimenez of Houston, Texas
.

 

Why
do your eyes hurt when you are tired?

Why do couch potatoes have such a bad reputation? While lying on the sofa perusing an Archie comic book or studying the impact of television violence on children by viewing Bugs Bunny cartoons, they are actually exercising what ophthalmologist James P. McCulley, of the University of Texas Medical School, calls “among the most active muscles in the body.”

Actually, your eyes contain three sets of muscle groups:

• Each eye has six
  extraocular muscles
  attached to the outside of the eyeball, which turn the eyes in all directions. The extraocular muscles must coordinate their movements so that both eyes look in the same direction at the same time.
  
• The
  sphincter and dilatory muscles
  open or close the pupils, defining how much light is allowed into the eye.
  
• The
  ciliary muscles
  attach to the lens inside the eye. When these muscles contract or relax, they change the shape of the lens, altering its focus.
  

Concentrated reading or close work provides a workout for these muscle groups strenuous enough to make Richard Simmons proud. Unfortunately, as in all aerobic programs, the saying “no pain, no gain” applies, as Winnipeg, Manitoba optometrist Steven Mintz explains:

 

The human eye is designed so that, if perfectly formed, it will form a clear image on the retina (at the back of the eye) of any distant object without having to use any of the muscles. In order to see closer objects clearly, however, each set of muscles has to
work. The extraocular muscles must turn each eye inward; the sphincter muscles must work to make the pupil smaller; and the ciliary muscles must contract to allow the lens to change to a shape that will produce a clearer image.

This minimal muscular effort is significant in itself. However, no human eye is perfectly formed and these imperfections will increase the amount of effort required. For instance, people who are farsighted must exert more than the normal amount of effort on the part of the ciliary muscles. Many people have extraocular muscle imbalances that force them to work harder. Virtually every person, as [he or she] approaches or passes the age of forty, suffers from a stiffening of the lens inside the eye, which forces those ciliary muscles to work even harder. Reading under poor light (either too much or too little) will cause the sphincter and dilatory muscles to work excessively.

Just like doing 100 pushups can cause the arm muscles to become pain [ed], so can the muscular effort…described above cause sore eyes. Add to this that after several hours of close work, all of your body’s muscles are going to be more fatigued, your level of tolerance or your pain threshold for sore eyes will be less than when you are fresh.

 

Ophthalmologists we consulted speculated that much of the eye strain attributed to tiredness is in reality caused by dryness. Dr. Ronald Schachar, of the association for the Advancement of Ophthalmology, notes that when one is tired, the blink rate slows down and the eyes are not properly lubricated. Close work also slows down the blink rate. Eye specialists are finding that workers at computer visual display terminals experience decreased blinking. This is one reason most consultants recommend stepping away from VDTs at least once an hour. While most of us are more than happy to rest our muscles after doing a few pushups, we expose our eyes to a marathon just about every day.

 

Submitted by Martin Nearl of Monsey, New York
.