Here we are at last!  Passion blog 15.  It has been a long road since my first metrology post at the beginning of the year, and I cannot say that I will miss writing these.  Either way, thank you to everyone who has read and commented.  For this last blog, I would like to make a few notes on the USCS and then close with some general metrology remarks.

Last Notes on the USCS

The US mass system is by far the most interesting portion of the USCS in my opinion, so I talked about it extensively at the expense of other topics.  The length measurements of the USCS have their own neat histories as well.  One unit to be aware of is the mil.  A lot of people just think this means millimeters, but one mil is actually one one-thousandth of an inch (1/1000 in).  The US also has a pretty complicated volume measuring system.  Today the most basic unit is the gallon of 231 cubic inches, which is commonly divided into four quarts.  Each quarter has two pints of two cups each.  Then, each cup has eight fluid ounces (the “fluid” differentiates from the mass unit).  A fluid ounce has two tablespoons of four fluid drams (compared to the apothecaries mass unit, which is why we add the “fluid”) each.  Finally, each fluid dram has 60 minims, which is about the volume of a drop of water.  The gallon also scales up to 31.5 gallons to a barrel (usually) and 63 gallons to a hogshead.

But of course it gets more complicated, for there are also the dry volume measures (these are used for measuring apples or wheat, but are not used in the kitchen) (Fig 1).  Here the dry gallon is defined as ⅛ bushel, where a bushel is a cylinder eight inches deep with a diameter of 18.5 inches (if you know your volume formulas, this is about 268.80… cubic inches to a dry gallon).  There are some other dry measures used in the food industry, like the peck (2 dry gallons), the dry quart, and the dry pint.  So, the next time you buy a pint of blueberries at the grocery store, know that it is actually 33.60… cubic inches, not 28.875.

Another interesting US unit is the acre (Fig 2).  This is used for measuring land area and covers a rectangle 66 feet wide by 660 feet long (or one chain by one furlong).  The reason it is interesting is that it derives its value from the area that a farmer could till in a day with a single plow.  That definition is not very useful today, but it is a neat piece of history.  One last unit is the degree Rankine.  This is essentially a direct answer to the Kelvin, so it defines absolute temperature.  To get to Rankine from Fahrenheit, use R = F + 459.67 (notice the similarities to C and K).

Closing Remarks

Once again, thank you to everyone who has read my blog over the past two semesters.  Metrology has been an interest of mine ever since I learned about the slug in ninth grade.  It has been great getting to write about this passion.  If, after reading these blogs, you find yourself with a similar interest, let me give you a few pointers.  NIST is my go to source for info on the SI system.  They handle the nation’s metrology and they have a ton of great articles.  They are a little lacking in “history of the USCS” information though.  For a while, my best source here was Wikipedia (I know), but the articles are not very well written and you never know what to trust.  That was when I stumbled upon an AMAZING book all about the development of the USCS.  I am about halfway through and cannot recommend it enough.  It is The Old Measure by Jon Bosak.  If you like what I talked about in my blogs, then it is a must read.  Veritasium also has a few good videos.  Finally, if you are looking to laugh, look into the Furlong-Firkin-Fortnight “system” of measure.  

That is all, and I thank you for reading my blogs.