If you think you're picking up strange vibrations at Gallery Joe, you're not alone. Jill O'Bryan's drawings can do that to you.

I know I felt a scraping vibration when I saw a work of hers in a group show there, "Very, Very Large Drawings," in 2009. I later learned that O'Bryan made that enormous drawing of geologic-looking markings by taking a roll of paper into the New Mexico mountains, laying it flat on a slab of rock, and rubbing its entire surface with graphite.

This time, walking through O'Bryan's first solo show at Gallery Joe, I sensed someone breathing.

It emanated from the drawings in the main gallery, in fact from one of the first works I saw, nm 7, a vertical drawing/painting in which rows of black and gray thumbprint-size brushmarks in liquid graphite on white paper vary in darkness. The visual effect is of syncopation, but also of a repeated physical effort varying in strength. Those marks, it turns out, record the number of breaths O'Bryan took while making this work.

Other drawings in the main gallery record O'Bryan's breathing but take different forms.

From a distance, a wall installation of small, square drawings on rice paper brings to mind an early Jennifer Bartlett enamel-on-steel-plate painting. Close up, each of O'Bryan's drawn images — black circles, X's, squares, rectangles and crosses — are made up of multiple graphite marks, each one representing a breath taken during the drawing's execution.

Other "Breath Drawings," such as 18,200 breaths between 4/1/2012 and 4/19/2012 record so many of O'Bryan's inhales and exhales that they've transformed the rice paper they're drawn on into what appear to be square, monochromatic pieces of a woolly patterned textile.

The familiar scraping vibration returned in the Vault Gallery.

Four of O'Bryan's new "Rock Drawings" are installed in this small windowless room, each 72-by-72-inch work a document of her interactions with a rock surface (the centrality of performance to all of O'Bryan's work is made clear in a video of her making one of these drawings). Seeing these images of raised (dark) surfaces and negative (white) spaces that represent ancient geological formations and that are simultaneously so similar to human skin and X-Rays of the human body — and knowing that they would likely never have been revealed but through the effort of O'Bryan — is as tempting to consider as their mysterious cumulative beauty.

Gallery Joe, 302 Arch St., 12 to 5:30 p.m. Wednesdays through Saturdays. 215-592-7752 or www.galleryjoe.com. Through June 2.

Warhol at La Salle

When the Andy Warhol Foundation for the Visual Arts started its Andy Warhol Photographic Legacy Program in 2007 and gave 28,543 photographs to 183 college and university museums, galleries, and art collections in the United States, La Salle University was a beneficiary of its largesse. The foundation's main request: that all of the institutions exhibit some or all of the works at least once every 10 years.

Hence, "Andy Warhol: Portraiture and the Business of Art," La Salle University Art Museum's first display of its Warhol holdings (and only one-third of them).

The theme — Warhol's penchant for portrait-making, cultivating and making money — is fleshed out in this tidy, handsome show by his color and black-and-white Polaroids of art collectors, models, and moguls, many of whom were never household names (Ahmet Ertegun, Marisa Berenson, Karl Lagerfeld, Cheryl Tiegs, and Sylvester Stallone are among the few recognizable faces here). Some of the photographs were used as studies for paintings, others were shot purely for fun.

The wall texts accompanying the photographs, written by the museum's director and chief curator, Klare Scarborough, who organized this show and cleverly inserted quotations from Warhol's diaries when appropriate to a particular image, are frequently more piquant than the images themselves. For example, for the text label next to two Polaroids of Lyn Revson, late wife of Revlon founder Charles Revson whose photographic portraits were studies for painted ones, Scarborough unearthed a typically Warholian diary entry from June 10, 1981 — which seems utterly borne out in these images of an aging sex kitten preening for the camera. "Lyn Revson called and said she loved the portrait, but that her cheekbones looked too fat. I knew she'd be trouble."

La Salle University Art Museum, 1900 Olney Ave., 10 a.m. to 4 p.m. Mondays through Fridays. 215-951-1221 or www.lasalle.edu/artmuseum@lasalle.edu. Through June 28.