The Laboratory

We are faced with a set of picture and phrase clues. There are four clue types: pictures of inventions, rebus, trivia, and cryptics. Each clue directs to a 19th-century French scientist who is one of 72 scientists whose name appears on the Eiffel Tower.

Each clue type fits the scientists on one of the four Eiffel Tower faces. The names are clued in alphabetical order. Once we identify each scientist, we realize that their names form dots and dashes on the Tower faces going clockwise, with the “final” face being the Paris face. These make Morse code for the phrase SAM M INVENTED. Sam(uel) Morse, is, of course, the famous inventor of the TELEGRAPH, which is the answer to this puzzle. (Submitting MORSE CODE yields a message to look at his other invention.)

The clued scientists and their face are as follows:

Clue	Scientist	Explanation	Face
Greenwich's rival has 135 markers dedicated to him	ARAGO		Ecole Militaire
	BARRAL	BARREL (E -> A)	Grenelle
	BECQUEREL	Sounds like MACKEREL (MA -> BE)	Grenelle
	BERTHIER	BERTH + PIER - P	Grenelle
Father of modern histology composed ABC hit	BICHAT	“Composed” clues anagram of “ABC hit”	Paris
Military engineer has a broken board	BORDA	“Broken” clues anagram of “board,” which is BORDA	Paris
Watchmaker with an awkward beer gut	BREGUET	“Awkward” clues anagram of beer gut, which is BREGUET	Paris
image of a hydraulic motor, which BRESSE invented	BRESSE		Trocadéro
	CHAPTAL	CHAPTAL was a prolific applied chemist responsible for the name of nitrogen, as well as various contributions to gunpowder, acids and sugar beets	Trocadéro
	CHASLES	CHASLES is the author of the theorem on conic pencil lines	Trocadéro
	CHEVREUL	A father of modern organic chemistry, he revolutionized soap and candle manufacturing and is also the author of the CHEVREUL illusion (on background)	Trocadéro
Contributed to modern thermodynamics by exploding a cryoplane	CLAPEYRON	“Exploding” clues anagram of “cryoplane”, which is CLAPEYRON	Paris
	CUVIER	Fossils cluing the Founding Father of Paleontology	Trocadéro
President of the French Academy of Sciences who developed logarithmic tables	DE PRONY		Ecole Militaire
	DULONG	This is the law of Dulong and Petit	Trocadéro
Geochemist who contributed to mining ore and porcelain manufacturing	EBELMEN		Ecole Militaire
	FIZEAU	Fizz + french water (“eau”)	Grenelle
	FLACHAT	Responsible for building the railway from Paris to St. Germain	Trocadéro
His simple device demonstrated the Earth's rotation	FOUCAULT		Ecole Militaire
	GIFFARD	Gifford (o -> a)	Grenelle
Ordained father of modern crystallography	HAUY		Ecole Militaire
	JOUSSELIN	“Sounds like” juice + Loretta Lynn	Grenelle
He predicted the position of Neptune from a twisted river reel	LE VERRIER	“Twisted” clues anagram of “river reel,” which is LE VERRIER	Paris
LEGENDRE polynomials	LEGENDRE		Trocadéro
This chemist is drunk - Lopez, eu	PELOUZE	“Drunk” clues anagram of “Lopez eu,” which is PELOUZE	Paris
Railroad engineer famous for each time he put on a lattice	PERDONNET	“each time” = PER, “put on” = DON, “lattice” = NET	Paris
Small French locomotive engineer	PETIET	Small in French is petit(e)	Paris
Geometrical mechanics inventor	POINSOT		Ecole Militaire
French fish with a probability distribution named after him	POISSON		Ecole Militaire
A moon crater is named after him, and, according to some, so is the ideal gas constant	REGNAULT		Ecole Militaire
	SCHNEIDER	Schnauzer (AUZ -> EID)	Grenelle
SEGUIN is the inventor of the suspension bridge	SEGUIN		Trocadéro
storm o->u	STURM		Grenelle
TRESCA designed the prototype 1 meter bar	TRESCA		Trocadéro
TRIGGER - G	TRIGER	X	Grenelle

Arranging the clued names by face of the Eiffel Tower, we get the following Morse message (dot = 1 name, dash = 2 consecutive names, one blank separates each symbol, two or more blanks separate letters):

Attributions

• Acid image is in the public domain from https://nara.getarchive.net/media/standardization-of-a-50-year-old-acid-solution-b728f5 in the US national archives
• Barrel image in public domain from https://freesvg.org/wooden-barrel
• Berth image is from https://commons.wikimedia.org/wiki/File:Upper_berth_of_RW25T_555505_%2820181107191050%29.jpg by user N509FZ under the Creative Commons Attribution-Share Alike 4.0 International license
• Candles image is a royalty-free image from https://www.pickpik.com/burning-candles-cc0-flame-lights-wax-101618
• Ear image in public domain from https://publicdomainvectors.org/en/free-clipart/Gray-ear-illustration/80532.html
• Fizz image is in public domain at https://www.pxfuel.com/en/free-photo-qadyz royalty-free use DMCA
• Fossil images are in the public domain at https://pixabay.com/photos/search/fossils/ and https://www.wallpaperflare.com/photo-of-dinosaur-fossils-on-gray-soil-skeleton-bones-excavations-wallpaper-wvwys
• Gunpowder image is from https://commons.wikimedia.org/wiki/File:Black_Powder-1.JPG by user Lord Mountbatten under the Creative Commons Attribution-Share Alike 3.0 Unported license
• Hydraulic gear motor is from https://ndla.no/subject:1:5a5cac3f-46ff-4f4d-ba95-b256a706ec48/topic:5d631e43-f324-41ad-9cb2-16a26fc391ac/topic:a322c488-0fef-4a61-8128-cfee23b95dc4/resource:1:123159 under Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
• Legendre polynomials image is from https://commons.wikimedia.org/wiki/File:Legendrepolynomials6.svg by user AkanoToE under the Creative Commons Attribution-Share Alike 3.0 Unported license
• Liquid nitrogen image is in the public domain at https://www.wallpaperflare.com/search?wallpaper=liquid+nitrogen
• Loretta Lynn image is cropped from https://commons.wikimedia.org/wiki/File:Loretta_Lynn.jpg by Scott Schram via Creative Commons Attribution 2.0 Generic license
• Mackerel image from https://www.fisheries.noaa.gov/species/atlantic-mackerel - public domain as a work of the US government
• Pier image is from https://commons.wikimedia.org/wiki/File:Pacifica_Pier_CA.jpg by user VirginiaBeach78 via Creative Commons Attribution 2.0 Generic License
• Railway tracks image is in the public domain at https://publicdomainvectors.org/en/free-clipart/Railroad-tracks-vector-image/30538.html
• Schnauzer image is from https://commons.wikimedia.org/wiki/File:Miniature_Schnauzer_R_02.JPG by user Lilly M under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation
• Soap image is in the public domain at https://www.rawpixel.com/search/soap%20bar?page=1&sort=curated&topic_group=_topics under CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
• Storm image is in the public domain at https://pixabay.com/photos/storm-thunderstorm-super-cell-3158852/
• Sugar beet image is in the public domain at https://www.rawpixel.com/image/3335615/free-photo-image-root-sugar-beets-animal as a free U.S. government image
• Suspension bridge image is in the public domain at https://openclipart.org/detail/316594/suspension-bridge-english
• Handgun (trigger) image is in the public domain at Image by https://www.vectorportal.comhttps://vectorportal.com/vector/modern-handgun/34029 under Creative Common Licenses
• Water image is from https://commons.wikimedia.org/wiki/File:Water_drop_impact_on_a_water-surface_-_%281%29.jpg by Jacopo Werther under the Creative Commons Attribution-Share Alike 2.0 Generic license