If we agree upon associating the Via Combust with the fall of the Sun and the Moon, then in a general way the entire signs of Libra and Scorpio will reflect the stricture.
In respect of either horary or astrology of the moment, my experience tells me that if both Sun and Moon are in Libra and Scorpio, so that either both luminaries are in their fall or in
mutual rejection and ABHOR in the location of the other - as with the Moon in Libra and the Sun in Scorpio, then the moment carries no light and the postulation is either false, running along an erronous path or the matter collapses completely.
In the case of women with nativities where the lights
ABHORED or rejected each other, I often found these women getting them selves into a tangle finding it difficult to receive themselves, their fruitfulness, their ability for recreation and reproduction - and often taking to
ABORTION. Hence, when I found this CAUTION in the chart I always paid extra attention and took the extra time to carefully sort things out and place things in their right context.
Now, if we determine that the exact fall of the Sun is at 18LI56 (
http://www.astronor.com/hours.htm ), then according to other strictures of old we also know that the last 3 degrees of a sign, or leading up to a cusp, induce a state of particular restlessness (I believe I go into detail on this in the article on the included link regarding the exaltation degrees of Venus and Mars). So something happens or changes in the 16th degree of Libra because this is 3 degrees ahead of the fall of the Sun.
Any significator in exact opposition of the Sun (+/- 2 degrees) will bring the matter signified by that planet to ruin (basic Lilly). But then the 15 degrees from the fall of the Sun to the fall of the Moon has an effect that is akin to the combustion. My experience with the first 15 degrees departing from the Sun and under the Sun's beams, is like something struggling to get out of starting blocks but that has not secured itself and come to an upright position. Like a new born baby that clings to life, although life has not yet established its firm grip and the infant is most vulnerable to crib death during the first 15 months after birth. This might prevent matters achieving the required velocity - hence the matter in question may lead no where and collapse.
The opposite side of the zodiac to the exaltation of the Sun and the exaltation of the Moon, hence the area of the luminaries' falls - this is the Via Combust. Adding the 3 degrees prior to the degree of the fall of the Sun as a situation of stress. That would suggest 16LI-4SC.
Now - the luminaries exhanging their detriments (Moon in Aquarius and Sun in Capricorn) also causes a situation of abhor. We may in time expand our understanding of technique as we get a better hold on the meaning of the planets
REJECTIONS, i.e. Mercury in Capricorn and Moon in Sagittarius, or Mercury in Cancer and Saturn in Pisces.
Olivia Barclay does quite briefly mention my investigations into this field on page 103 of her book "Horary Astrology Rediscovered", (c) 1990.
Andrew