On Ptolemy climes

Question

Reading Dante's Comedy, I was interested in understand a little bit how medieval geography worked, so I decided to have a look at Edward Luther Stevenson's translation of Ptolemy's Geographia. I've also read the review of this book that Audrey Diller wrote in 1935, so I know it's not precisely the best translation of Ptolemy's work, but it's better than nothing.

In particular, in the XXVII canto of the Paradiso, Dante mentions the first clime, so I was curious to understand what climes exactly were.

Comparing the explanation of parallels used in the delineation of maps and the reproduction of maps that are at the end of the book, which in fact are not the maps of Ptolemy, but the 27 Ptolemaic maps as revised by Donnus Nicolaus Germanus in the XV century (in particular, they are designed using a different projection), I have seen the following:

• The first clime is located on the parallel through the Meroe island.
• The second clime is located on the parallel through Syene.
• The third clime is located on the parallel with a latitude of 30° 20'.
• The fourth clime is located on the parallel drawn through Rhodes.
• The fifth clime is located on the parallel with a latitude of 40° 55'.
• The sixth clime is located on the parallel with a latitude of 45°.
• The seventh clime is located on the parallel with a latitude of 48° 30'.

I've also read that the part of the earth that was considered as inhabited by humans was bounded on the south by a land which was unknown which encompasses some part of Africa and the Indian Ocean (the "Indian sea" at that time). To delineate maps, the southern boundary of the inhabited earth was defined by the parallel that has a latitude of 16° 25' south of the equator. Now, my question is: was this parallel considered the southern limit of the first clime?

At this link you will find the Latin inscription on such parallel on the map of Africa: I can't understand what it says.

Update:

I've found this illustration in the book, but I have no idea where it comes from, but I think it's probably from the Renaissance, since the source of Stevenson's work seems to be Renaissance Latin translations of the Geographia:

So I now suspect that the southern limit of the first clime was the equator and that the parallel with a latitude of 16° 25' south of the equator was defined at Renaissance (?) as the Antidiameroes, that is, the boundary of some kind of first clime in the southern hemisphere. Is that correct?

Answer 1

Originally, the Greek word κλῐ́μᾰ means “slope, incline, inclination,” and has nothing to do with the modern meaning of the word (long-term weather). Ptolemy defined the seven climata by the length of the longest duration for the day (defined as the period when the sun is visible in the sky, and as opposed to night, when it’s not visible; the combination of both day and night periods [24 hours] is a nycthemera).

One clima differs from the next by a half-hour of day per nycthemera. The map you link to does have mentions of the duration of the day: for example, the second line from the bottom says “3[?] paral[x] habet maximũ diem hora[x] 12½¼” (where the [?] means I’m not sure it’s a 3; the [x]s are characters I can’t reproduce; and ½¼ is to be read as ½ + ¼ = ¾).

Ptolemy believed that the equatorial regions of the Earth were too hot to be inhabited, so he counted only “habitable” climata. The first one, as you pointed out, is the parallel of Meroe, where the longest day (June solstice) lasts 13 hours. Then for Syene, the longest day would last 13½ hours, and so on, until the clima of the Borysthenes (modern Dniepr river in Ukraine) at 48° 32′ and a longest daytime of 16 hours.

As for the mention of climata in the works of later authors, most of them, if not all, do indeed correspond to the Ptolemaic climata.